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Dermatology James O. Noxon, DVM; Diplomate ACVIM (Internal Medicine) Iowa State University Dermatology Diagnostics Introduction "First collect the facts. You can distort them later." ...Mark Twain The value of diagnostic procedures commonly used in veterinary dermatology is dependent upon 1) the technique, and 2) the interpretation of the results. The accuracy of a diagnostic test is only as good as the technique used to perform the test. Equally important is the interpretation of the results by the technician or clinician. We will discuss techniques and keys to maximizing the value of common diagnostic procedures used in veterinary dermatology. "Diagnostic" Procedures Signalment The signalment of the patient (age, breed, sex) should always be consciously noted, since certain breeds are predisposed to certain dermatologic conditions. A list of breeds and their associated dermatologic problems may be found in the textbook, Small Animal Dermatology. History The clinical history is the single most important diagnostic procedure performed in each case. The history should be obtained in a relaxed environment and should be written down. It is helpful to have a history form available for the client to fill out prior to or while they are waiting for their appointment. The form will help when records are reviewed and when the patient is seen for recheck examinations. The history includes:
Each patient should receive a complete physical examination. Dermatologic Examination After the general physical examination, the skin should be systemically examined. A "hands-on" examination must be performed. The dermatologic examination should be complete and include examination of the entire hair coat, careful palpation of the skin, careful examination of the skin surface over several areas of the body, visual examination (otoscopic) of the external ear canals, and inspection of the foot pads. In many cases it is helpful to clip hair from the patient so that specific lesions may be seen more clearly. It is also helpful to have a form for the medical record, on which lesions may be drawn and recorded, as well as other information. Skin Scrapings for Parasites The skin scraping should be done on all animals with dermatologic disease. They are especially helpful in diagnosing or ruling out parasitic diseases. Materials: Necessary supplies include a #10 scalpel blade, mineral oil, glass slides, clippers and a microscope. The scalpel blade should be wiped clean and saved for future use. Dull scalpel blades cause less skin trauma. Procedures: The area to be scraped should be free of hair or clipped. The skin should be squeezed gently and released. A drop of mineral oil is placed on a glass slide. The blade is wiped in the oil and then used to scrape the surface of the skin, holding the blade perpendicular to the skin surface. An area approximately 2x2 cm should be covered on each skin scraping. The material collected on the scraping is then transferred to the slide and examined under scanning and 10x objectives. Keys to success:
Skin Scrapings / Impressions Smears/Tape Preparations for Yeast (Malassezia spp.) Skin scrapings/smears for Malassezia are performed whenever yeast are suspected as a primary or secondary cause of pruritus, scaling, erythema, or seborrhea. Materials: A #10 scalpel blade, glass slides, adhesive microscope slides or clear waterproof adhesive (i.e., Scotch) tape, clippers, cotton swab, a microscope slide, microscope, and appropriate stains. Adhesive microscope slides (Duro-Tak) are available from Delasco, Dermatologic Lab & Supply, 608 13th Avenue, Council Bluffs, IA 51501, 1-800-831-6273 or 1-888-335-2726. Procedure:
Noxon's Scale for Malassezia (Skin) 0 No yeast seen on slide 1 Few yeast (1-5) seen on slide 2 One yeast seen every 4-8 oil immersion fields (1000x) (Several on slide) 3 One yeast seen every 2-3 oil immersion fields 4 One or more yeast seen every oil immersion field Note: The scale is deliberately vague....It is used to help determine improvement on recheck evaluations. A 2+ or greater is considered significant by the author, though ultimately significance is based on numbers and clinical information. Trichograms (hair "plucks") The trichogram is useful to evaluate the integrity of hair shafts and also serves as a test for demodicosis and dermatophytosis. Materials: Forceps, mineral oil, glass slides, cover slips, and a microscope are needed. Procedure: Hair samples are taken from patients by using mosquito forceps or other forceps to firmly grasp several hairs and firmly pull them (i.e.,"pluck) from the follicle. The hair samples should be placed in a drop of mineral oil on a microscope slide and them covered with a cover slip. The slide is examined immediately. Hairs are examined for 1) type: primary vs secondary, 2) structural damage to hairs supporting the presence of pruritus (e.g., fractured hairs from chewing) or other hair shaft abnormalities (various diseases), 3) evidence of dermatophytosis (e.g., hyphae or spores), 4) ectoparasites, primarily Demodex species (also Cheyletiella spp. eggs, nits, or fur mites), 5) the stage of hair growth (anagen vs telogen), and 6) pigmentary abnormalities (e.g., clumping of melanin associated with some follicular disorders and color dilution alopecia). Comments: Abnormalities may often be subtle and a trichogram may vary from animal to animal and at different seasons. However, gross abnormalities or the presence of parasites or infectious agents may provide significant information to the general practitioner. It is an excellent method to find Demodex spp. mites, especially in cats. Keys:
Fungal cultures should be run on all dermatology cases; especially if there are circular, crusty or scaly lesions, or if broken hairs are present. Materials: Forceps, culture media, glass slides, stains, cover slips and a microscope. Procedure: Hair samples, crusts from lesions taken by skin scraping or nails should be collected and gently applied to the surface of the selected culture medium. Broken hairs are preferred for culture, if present. Generally 8-20 hairs are cultured, spread out over the medium. The medium and samples should then be incubated at 30oC and 30% humidity. Samples should be observed daily for growth for at least 10 days and then periodically for a total of four weeks. Samples may be incubated at room temperature if the humidity is controlled. After the colony grows on the medium, hyphae should be teased apart and placed on a glass slide with a stain such as lactophenol cotton blue, and a cover slip added. The sample should be examined microscopically and the fungus identified. Alternatively, a piece of clear acetate tape can be touched to the surface of the Sabouraud's Dextrose Agar colony and placed on the slide as a coverslip over the drop of stain. This can then be examined under 10X and 40X. Keys:
Following the patient's response to therapy can be an effective diagnostic tool. Whenever drugs, medications, or food are used without a definitive diagnosis, the treatment should be considered a diagnostic procedure. Clients should be informed of the value of a trial...and should be carefully instructed to watch for improvement and to record information. The most common diagnostic trials are performed with:
Summary Proper application and performance of these diagnostic procedures will greatly enhance the accuracy of diagnosis in dermatology cases. Veterinary technicians should be properly trained to perform these procedures. There is no substitute for knowledge, diligence and meticulous care in the application of proper diagnostic procedures. Cytology And Biopsy Techniques For Dermatology Introduction Cytologic and histopathologic examinations of the skin are important diagnostic tools. There are three important aspects of these tests: 1) selection of the proper lesions or locations from which to collect samples, 2) proper collection of materials, and 3) interpretation of the material. We will focus on selection of lesions and proper collection techniques for cytology and histopathologic evaluations and spend a little time discussing interpretation of cytologic preparations of the skin. Cytology Cytology is defined as the collection of cellular material and fluid for microscopic examination. This procedure is heavily used in all aspects of medicine, but is of tremendous value in dermatology cases. The skin is an external organ, and thus, the lesions we must evaluate are readily accessible for this diagnostic procedure. It would be a great waste NOT to perform cytology on our cases. In fact, it is indicated in almost all patients presenting with skin disease. Cytology provides the veterinarian with useful information about the etiology, pathogenesis, and severity of skin diseases. Cytologic techniques are very useful as a monitoring tool in dermatology cases, for example to monitor the presence of infectious agents in the skin or ears following therapy. Lastly, cytology is a cost effective diagnostic procedure. It will generate income for a veterinary practice (while providing essential information for managing patients. The veterinary technician is a key individual in the procedure. Technicians can collect material, process the sample, and can evaluate most samples after some basic training. The results, however, are only accurate and valuable if the technique is properly performed. My experience is that technicians are more enthusiastic and reliable in the performance of these tests. Indications Cytology is indicated in ALL dermatology cases. It is most helpful in determining the cause of pustules, papules, nodules, tumors, draining tracts, chronic ulcerations, or plaques. When examining the sample we are specifically looking for:
For the most part, cytology is a very cost effective diagnostic procedure. Other than a quality microscope, the only supplies required are swabs, syringes, needles, glass slides, a camel hair brush (wait and see!), and various stains. Several stains are available for cytology. Romanowsky stains such as Wright's stain, and modified-Wright's stains like Diff-Quick StainR are easily and quickly performed. They are excellent when permanent slides are desired. Supravital stains such as New Methylene Blue are also easy and rapid. Each clinician should choose a stain that he/she is comfortable with and become accustomed to its staining qualities. Several techniques may be used to obtain samples: 1) Fine-needle aspirate; 2) Impression smears made directly from the surface of cutaneous lesions &impression smears made from cut surfaces of lesions (e.g., tumors) removed from the skin; 3) Scrapings of tumors or nodules; 4) Lancing pustules or papules to remove contents for examination; and 5) Swabs made using cotton-tipped applicators. Each technique has advantages and is best suited for specific lesions. Table 1. Indications for Various Cytological Collection Methods
Samples may be distributed on a slide by non-traumatic imprints, "squash" preparations or brush cytology. In the "squash" technique, the sample is placed on the slide, and then another slide is placed over the slide with the sample. No pressure should be placed on the sample! The top slide is then gently pulled away from the slide with the sample, leaving the specimen distributed across the slide. 
Figure 1. "Squash technique for sample distribution. In brush cytology, the sample is placed on a clean glass slide and then spread out using a camel hair brush or nylon artists brush. The brush is then rinsed well with tap water prior to each use and after each use to prevent contamination. When performed properly, this technique gives single cell layer distribution on the slide, with a minimum of trauma to the sample. Slides should then be fixed and stained. One slide should be left unstained in case a special stain is needed. There are multiple options for staining cytologic specimens. Most clinicians prefer a Romanovsky type stain (Wright's stain, Giemsa stain, or modified Wright-Giemsa [Diff-Quik] stain). New Methylene Blue stain is a supravital stain that is especially good at providing nuclear detail. Slide Examination The entire slide should first be examined under a low (scanning) power. On most microscopes the lowest power is 40X (a 4 power objective), however, lower power objectives (e.g., 2X) are available. The scan is performed to evaluate the staining of the slide, to identify areas that should be examined more closely, and to identify large structures (e.g., foreign bodies, hyphae, & Demodex mites) that may be missed under higher power. After the scan is completed, the slide should be examined using low power (10X objective) and oil immersion (50-100X) objectives. Tip 1: Always keep one hand on the fine focus knob while scanning a slide. You should be slowly moving that knob back and forth, adjusting the focal plane to allow you to see materials at different depths of the slide. This is especially critical on cutaneous impressions and slides when the material is somewhat thick. Tip 2: Most microscopes have a "high dry" objective, usually a 40X objective giving a total magnification of 400X. These objectives are designed to work best when the slide has a cover slip. Otherwise the image will be slightly blurred. So....place a drop of immersion oil on the sample, then add a cover slip, if you use this objective....you'll be impressed with the difference. Submitting Samples for a Second Opinion It is often useful to have the slide evaluated by another individual and/or to send the sample off for evaluation by a specialist in cytology. In general, it is recommended to contact the individual to whom you are intending to send the material, and ask their preferred methods of handling and submission. Most cytologist would like to receive 1-2 unstained, unfixed slides, and 2-3 Romanovsky-stained slides for their review. Some prefer to have the specimen (aspirate or fluid) sent in an EDTA blood collection tube, as well. Fluid specimens should have slides made as soon as possible for examination, even if the fluid is to be sent away for evaluation. Slides may be placed in a plastic or cardboard slide mailer, taped closed, and wrapped in bubble wrap or a padded envelope for mailing. The package should be labeled as "fragile" and/or as "glass". It is always important to include a brief history of the problem, a drawing indicating the source and location of the lesions, and other appropriate data. Remember, cytology is only one piece of the puzzle. Ear Cytology Cytology of debris collected from the external ear canal is a useful and valuable technique to assess current status and monitor response to therapy. Cytology of material collected from the ear should be performed every time a patient is examined for an ear problem. Materials required for this procedure include cotton swabs, glass microscope slide, matches, Diff Quik7 stain, and a microscope. To collect representative material from the ear, a dry cotton swab is inserted into the external ear canal and advanced slowly and gently. The goal is to reach the horizontal component of the ear canal. This is made easier by grasping the pinna and gently pulling the ear out and downward. The swab is slowly rotated during the process to help collect debris and exudate. The swab is then rolled out on a slide. TIP: I always examine both ear canals. I will place samples from both ears on the same slide, material from each side on opposite halves of the slide. This saves time when examining the slide. The slide is heat fixed by holding a match or lighter under the slide for 2-3 seconds. The slide should be come warm, not hot! TIP: All slides that have greasy materials on them should be heat fixed to help adhere the material to the slide. Slides should then be stained using the preferred stain. Note that even with heat-fixation, much of the debris will be lost during the staining process. Therefore, if Diff-Quik stain is used, the process must be very, very gentle. Also, debris and infectious agents will contaminate the stain. It is necessary to change stain regularly (at least weekly) to prevent misinterpretation of results. After staining, examine the slide under oil immersion for the presence of bacteria (rods and cocci) and yeast (Malassezia sp.). Bacteria are only occasionally seen in normal ears; Malassezia are occasionally seen as well (1-2/oil field is normal). Epithelial cells are usually seen in small numbers. The relative number of bacteria, yeast and epithelial cells should be recorded using an arbitrary scale (i.e. 1-4+). The presence and relative number of neutrophils should also be noted. Neutrophils without bacteria suggest a hypersensitivity reaction to medication being placed in the ear (neomycin and propylene glycol being the biggest offenders). Practical Application As we look at clinical lesions on a patient, it is crucial to be thorough and to consider the following:
There are a few important keys to maximize the value of the skin biopsy as a diagnostic procedure. The first is to select the proper lesions. A good rule-of-thumb is to take a piece of everything that looks different. Second, proper technique in collecting the sample and submitting it a manner that will not negatively affect the sample is very important. Third, it is crucial to send your samples to a dermatohistopathologist…or at least someone who is interested in skin diseases and who will embrace the challenges that skin biopsies bring. In addition, it is necessary to remember that a skin biopsy is only one more "piece of the puzzle". It is frequently NOT the definitive test in a skin disorder. Histopathologic evaluation of the skin may not provided you with a definitive diagnosis, yet it will still help you to rule out certain skin problems and bring you closer to a final diagnosis. While this may not be palatable to some clients (and veterinarians, I suppose), it is occasionally necessary to repeat a skin biopsy, since skin conditions do evolve and change over time. A second biopsy may provide a definitive diagnosis, where a first biopsy was non-specific. That is the nature of dermatology. Indications Histopathologic examination of the skin is essential to confirm the clinical diagnosis in many cases. It is most useful in autoimmune skin diseases, neoplastic diseases, but will also provide key diagnostic information in allergic skin disease, parasitic infestations, endocrine and metabolic disorders, congenital dermatoses, and degenerative diseases. Skin biopsy may be necessary to confirm cutaneous manifestations of skin disease, and may in fact provide the key diagnostic information to direct the clinician to a systemic disease process. HOWEVER, it is very important to understand that histopathologic examination of the skin provides only one more "piece of the puzzle" in most dermatology cases. Excessively high expectations will lead to frustration on the part of the veterinarian and the client, if the value of skin biopsy is not carefully explained. Material & Methods The surgical biopsy pack should include needle holders, mosquito forceps, tissue forceps, scissors, and scalpel handle. Many skin biopsies are performed using "punch" biopsy instruments, which will speed up the process in most cases. Four (4) and six (6) mm biopsy punches will suffice in most cases. Ten per cent (10%) buffered formalin solution is used as the standard fixative. Local anesthesia (often with some analgesia/sedation) is acceptable for most skin biopsies, depending on the demeanor of the patient. General anesthesia is recommended for biopsy of the pinnae, foot pads or distal extremities, nasal planum or facial region, and periocular skin. Different clinicians have different perspectives on the amount of anesthesia and analgesia needed for different animals. When a local anesthetic is used, approximately 0.5-1.0 ml of 1-2% lidocaine (with or without epinephrine) is infiltrated under the area to be sampled. The injection needle for the local anesthesia should never pass through the area to be collected. Tips for maximizing value of skin biopsies:
There are many skin disorders that affect the nasal planum, especially the autoimmune and infectious diseases. Surgical biopsy is critical to make a diagnosis. Since the skin in this area is lying over cartilage, our goal is to NOT damage the underlying cartilaginous tissue. This primarily is done simply by making cautious incisions with either a scalpel blade or punch biopsy instrument. Some comments:
The inner surface of the pinnae is a difficult place to biopsy due to the tightly adhering nature of the skin to the underlying cartilage and the very thin skin in the area. Damage to the underlying cartilage during the biopsy process may result in complications, such as disfigurement or aural hematoma. To avoid damaging the cartilage:
General anesthesia is usually necessary to biopsy the foot pad. In addition, we place a tourniquet around the leg to be biopsied to help reduce hemorrhage during the process. No surgical scrub is performed, although hair is clipped around the edge of the lesion as much as possible. An alcohol rinse may be used to clean the surface. Tips for foot pad biopsy:
Summary Cytology is one of the most useful diagnostic tools for dermatology. Virtually every dermatology case presents with multiple opportunities for cytologic evaluation….and the information that cytology provides, is often the key diagnostic information that marks the therapeutic path for that patient. Proper application and performance of these diagnostic procedures will greatly enhance the accuracy of diagnosis in dermatology cases. There is no substitute for knowledge, diligence and meticulous care in the application of proper diagnostic procedures. Remember to select the best locations for cytology or skin biopsy, use good technique, then send specimens (when necessary) to a train and interested pathologist. Appendix Tuning the Microscope for Maximum Clarity (Kohler Illumination) Step 1
Making the Most Out of Allergy Testing Overview The American College of Veterinary Dermatology task force on canine atopic dermatitis published a collection of papers that review various aspects of atopic disease. The task force reviewed fundamental concepts in clinical diagnosis of canine atopic disease and concluded:
There are two general types of allergy tests available for common use: the intradermal allergy test (IAT) and serologic tests. Intradermal allergy testing has been used for decades in veterinary dermatology, and since this type of test was the first available allergy test for animals, it has long been considered the gold standard for allergy testing. The theory of intradermal testing is based on the understanding of the pathogenesis of atopy, which in a simplified description, is overproduction of IgE in genetically-susceptible animals following exposure to an allergen (i.e., sensitization). The IgE then circulates and is bound to tissue mast cells, which degranulate upon subsequent exposure to this allergen. In the IAT, small amounts of allergen are injected intradermally.... (Why intradermally? Because that is the location of the mast cells in the skin.) ...which, IF antibody against those allergens is present on the mast cells, will cause degranulation of the mast cell with release of preformed mediators of inflammation. The net result in the skin is leakage of fluid from capillaries and inflammation, causing a classical wheal and flare reaction. In essence, this test is attempting to detect allergen-specific IgE on mast cells (in vivo). Serologic tests are detecting allergen specific IgE that is located in the blood (or serum). IgE will circulate in the blood until it is removed from circulation and/or bound to tissue mast cells. This test may employ one of several different (but similar) methodologies: radioallergosorbant testing (RAST), enzyme-linked immunosorbent methods (ELISA), or variations thereof. In addition, some commercial laboratories have made modifications to the test looking for specific parts of the IgE molecule or by varying other aspects of the testing process. Allergens It is necessary for the veterinarian to have a working knowledge of allergens that affect dogs and cats. There is extensive literature directed towards human dermatology that available on the topic. Fortunately, the concepts and principles of allergen management are identical for all species. Many allergens, especially pollens and molds, will cause seasonal disease. There can be a good deal of cross-reactivity between some allergens in similar categories. For example most of the trees in the same family have significant cross reactivity, allowing the testing of one species in that family. There are notable exceptions, such as Box elder and maple, and cottonwood and poplar. There is probably significant cross reactivity in many insects, but most allergists test for these separately. A good way to help you (the practitioner) to determine the most significant allergens in your area is: 1) Ask the various allergen suppliers for a list of the important allergens in your region. Much of this information can be found in various locations on the internet. 2) Ask your local human allergist for a list of the allergens to which they test their patients. This should give you a pretty good idea of the clinically significant allergens in your area. 3) Ask you local agricultural extension office (or university) to review the list of plants and molds felt to be significant in your area. They often have some interesting insight. The time of day may influence clinical signs. Most pollen levels and mold levels rise during the heat of the day and are reduced following rain. Increased wind can also increase the pollen / mold circulation as it picks up spores in the environment. Preparation for Allergy Testing It is widely accepted that several medications may interfere with the allergy tests. Glucocorticoids are the most influential, however, antihistamines, fatty acids, antidepressants, and food additives may be able to dampen that allergic response to IAT. Their effects are less clear on serologic testing, but clinical impressions suggest that it is prudent to withdraw from these medications for serologic testing. Recommendations vary among dermatologists and commercial laboratories offering these tests. Our recommendations are:
Regardless of the type of allergy test that is performed, it is important to objectively look at the results. It is not sufficient for the veterinary practitioner to read the allergy interpretation from a commercial company and (naively) place the patient on immunotherapy based on the recommendations. The results must be interpreted with knowledge of the clinical history, clinical features, and past therapy. Some key points are:
Hyposensitization (Allergen-specific Immunotherapy) Allergen-specific immunotherapy (ASIT; hyposensitization) involves taking substances that cause an exaggerated response in an animal when exposed by cutaneous exposure or inhalation, and administering the substance subcutaneously. This logically seems to be a bad idea! The key is a controlled exposure. The goal is to alter the patients response, in theory causing production of IgG, which will block allergens in the body before they reach the mast cells. Hyposensitization may have other mechanisms to induce change in patients, but they are not clear. Allergens identified by allergy testing (and considered relevant) are mixed into a hyposensitization solution, often called a vaccine. There is some evidence that suggests that some allergens should not be mixed together, as they may inactivate the other allergens. The most significant of these is the addition of molds to general mixes, since the proteases found in some molds may reduce allergenicity of pollens. There remains considerable debate about the maximum number of allergens that can be used for hyposensitization at one time. Some allergist limit the total number to 12-14 per vial,: others have prepared vaccines with 30-40 allergens per vial. The main consideration is the net concentration of any given allergen in the solution. The more substances that are included in a limited final volume (about 10 ml), the less of each allergen that can be included (the more dilute). However, most studies (which are few) appear to support the concept that more can be used. For large numbers of allergens (greater than 14-20) a second vial is recommended, so that the dilution is less significant. This does, of course, increase the cost of the solution. Owners are taught to administer the injections subcutaneously. They should give injections on their own pet prior to release from the hospital...if the owner can=t give the injection in your presence, there is a good chance they will not give them properly at home. A prepared treatment schedule with a checklist for injections is provided. We recommend injections are given at a time of day when their veterinary clinic is open for business, in the rare event of an adverse reaction (e.g., anaphylaxis). Treatment Schedule Many treatment schedules are used by various allergist / commercial allergy companies. The concept is that small amount of low concentrations are given initially, with slowly increasing concentrations and volumes until a maintenance dose is reached. The schedule MUST be formulation on an individual patient basis....taking in to account the patient, the severity of the allergy, the clients schedule, and the allergens. In most regimens, the higher concentration of allergen is around 20,000 PNU/ml...and is given weekly. We recommend continuing the dose weekly for several weeks (up to 9-12 months of therapy) or until the owners feel a satisfactory result has been achieved. One HUGE source of treatment failure when commercial schedules are followed, is premature reduction in dose. We ask for owners to commit to 9-12 months of therapy, regardless of the clinical benefit. At that time, the patient is re-evaluated for efficacy of treatment. Schedule: There are many different treatment schedules used by dermatologists worldwide. The principle is that we expose the patient to increase amounts of allergens (to which the patient is allergic) over a given period of time. It is during this "buildup" of allergen that the beneficial effects of hyposensitization are seen. It is important to understand that individual patients vary in their response to hyposensitization, both in terms of success, and speed of the response. Thus, there is no one perfect hyposensitization schedule appropriate for all patients. Hyposensitization treatment programs should NOT be based on the schedule defined by an outside company. It is fine to use their treatment recommendations as a start….but the program should be adjusted based on the patient's response. In traditional ASIT, patients are induced over a 30 day period of time and injections are given weekly until maximum benefit has been achieved. Once the owners (with your help) determine that the maximum benefit has been reached, the frequency of the injections can be slowly increased...initially to once every 10 days, then if the patient does well for an additional month, to every two weeks, etc. Most atopic patients require injections every 7-14 days during their peak season and every 14-21 days during off times. Table. Typical Hyposensitzation Schedule used for dogs
Administration of medication to control pruritus (e.g., glucocorticoids) does not appear to reduce the effectiveness of therapy, and is generally necessary until the injections provide some relief. Clinical improvement is most often seen between 2-6 months, and is quite variable. Rush Immunotherapy Protocols have been developed where the patient is given the induction doses in one day. In most protocols, injections are administered subcutaneously every 30 minutes. The patient is generally pretreated with antihistamines and the patient is monitored closely for adverse effects. Therapy is suspended at the higher dose that is tolerated by the patient and those doses are administered weekly for maintenance. Adverse reactions may include anaphylaxis, urticaria, or increased pruritus following injections, which was reported in one study in 27% of the patients. The pruritus does respond to prednisone. Some studies have shown a more rapid onset of benefit and a slightly higher success rate with this therapy. However, in one study, the time required to achieve 50% improvement in patients was not different from traditional immunotherapy. The advantage this protocol provides is an option to induce the patient in the hospital for those clients who can not or will not be able to follow the induction schedule over one month. Success with a similar protocol has been reported in a study with very low numbers of cats. Treatment Failure What about the 10-30% of patients that fail to respond to ASIT? If the patient is not responding and/or the client wishes to discontinue the therapy, it is wise to decrease the injection amounts by 0.1-0.2 mls every week (over a ten week time period). Recent studies have shown that some dogs will show improvement as the doses of solution are reduced! Reductions are done by approximately 25% of the original weekly dose each month. It is not recommended to start with lower doses, but the process of ceasing therapy provides a perfect situation for slowly decreasing the amount given per injection. Approximately 10-33% of dogs managed in this manner will show significant improvement. Trouble shooting
Allergy testing can be a highly useful procedure to identify allergens and provide information to allow for allergen specific immunotherapy (hyposensitization). It is helpful to understand the limitations of these tests and the mechanisms, so that we can better discuss the therapeutic options with our clients. References A complete list of references available upon request. Management of Autoimmune Skin Disease General Information on Autoimmune Disease The pathogenesis of autoimmune disease involves genetic, environmental, and hormonal influences. The genetic evidence is very clear in some diseases, such as systemic lupus erythematosus (SLE) and dermatomyositis. In other conditions, the disease clearly has a familial basis (breed predilection), but the mode of inheritance is unclear. One example of this is uveodermatologic syndrome, seen in Akitas. It is quite likely that many, if not all, of our other autoimmune diseases have some genetic basis for their development. The environmental clearly influences the development of some autoimmune conditions. Ultraviolet radiation is known to exacerbate both discoid and systemic lupus, and may also affect pemphigus. Infectious agents in laboratory animals can act as triggers, inducing an autoimmune condition is an otherwise genetically predisposed, but healthy, animal. There has long been speculation that infectious agents or even vaccines may induce autoimmunity in a susceptible animal. Hormonal influences in autoimmune diseases are clear in humans, where more women than men develop autoimmune disease (e.g., SLE). However, it is not clear in animals...and in fact, SLE has been reported to develop in equal numbers of male and female dogs. Diagnosis Autoimmune diseases are diagnosed by clinical features of the patient, including history and physical examination findings, cytologic evidence of autoimmune disease in some cases, microbiological findings (usually negative results), various immunodiagnostics, dermatohistopathology, and demonstration of autoantibody within tissue. To the novice, all autoimmune skin diseases look alike. However, with some experience there are clear differences in their distribution, types of lesions, and other clinical features. Cytology is used primarily in those pustular diseases, such as pemphigus, where the finding of acantholytic keratinocytes is a strong indicator of that disease. Immunodiagnostics, such as protein electrophoresis and antinuclear antibody titers, are helpful, but not pathognomonic for any given disease. Histopathologic examination of the skin is the most definitive diagnostic procedure for the vast majority of autoimmune skin diseases. The keys to an accurate diagnosis are lesion selection, biopsy techniques, and interpretation of the biopsy (the pathologist). Demonstration of autoantibody in the skin, through the use of direct immunofluorescense testing or immunohistochemical staining techniques is a useful procedure, but is not necessary in most cases. Philosophy of the Treatment of Autoimmune Skin Disease In the overall concept of treatment / control of autoimmune disease, we can direct efforts at either control of the affector (induction) part of the immune response, OR control the effector phase (inflammation). Control of the induction component of the immune response are primarily attempting to disrupt the normal production of the clone of lymphocytes that is responsible for the production of cytokines or antibodies directed against normal tissue. These are usually cytotoxic drugs, such as alkylating agents or antimetabolites, although glucocorticoids will have this effect with long term, high dose therapy. In general, it is best for the patient to be aggressive early, then after induction is reached, back off the medications as quickly as possible. Aggressive, rapid induction will reduce the long term side-effects cause by cumulative doses of chemotherapeutic drugs, such as glucocorticoids. Aggressive therapy will still lead to side-effects that may be undesirable, however, once induction is achieved, these doses can be radically decreased, resulting in less long-term adverse effects! Drugs Used to Control Autoimmune Skin Disease Glucocorticoids are the most common group of drugs used to manage autoimmune skin disease. They work by paralyzing receptors (e.g., Fc receptors on macrophages), blocking chemotaxis of inflammatory cells to tissues, and by interfering with production of autoantibodies. The latter probably takes a minimum of 2-4 weeks to occur. Any glucocorticoid can be effective in managing autoimmune disease, though prednisone or prednisolone are considered drugs of choice because they can be administered orally, are relatively inexpensive, have moderate potency, and have a relatively short half-life (to allow sparing the HPA axis with alternate day therapy). The so-called Aimmunosuppressive@ dosage is approximately 2.2 mg/kg daily. Potential side effects: polydipsia, polyuria, polyphagia (and weight gain), panting....more severe reactions include gastric ulcers, pancreatitis, secondary infections. The drug is initially given daily for induction...then switched to alternate day therapy for maintenance....decreasing total dose by 20-25 % every 2-4 weeks. Cytotoxic drugs, such as alkylating agents and antimetabolites are used to decrease antibody production. This therapy probably takes 2-4 weeks (minimum) to effectively decrease antibody production. Cyclophosphamide is an alkylating agent commonly used to manage autoimmune diseases, though rarely for skin disease. It has many possible adverse reactions, including: bone marrow suppression, gastroenteritis, transitional cell carcinoma, hemorrhagic cystitis, and alopecia. It is classified by the EPA as hazardous waste. Chlorambucil is another alkylating agent that is considered milder than cyclophosphamide. It has fewer side-effects, including myelosuppression and anorexia...making it an excellent drug to be used in cats. Azathioprine is an anti-metabolite (purine analog) agent. It is given as a dosage of 1-2 mg/kg daily for induction, then tapered off during maintenance therapy. Possible adverse effects include gastroenteritis, pancreatitis, myelosuppression, and neuromuscular blockade (cats). Cats will have more adverse reactions (myelosuppression, neuromuscular blockade) than dogs, and therefore is not recommended by the author for use in that species. If used, the dosing should be 1 mg/kg every other day. Chrysotherapy is the term for the use of gold salts. Gold is conjugated to other substances, such as sugar and is available in injectable (e.g., aurothioglucose-Solganol, gold sodium thiomalate- Aurulate:Pasdena) and oral formulations (Auranofin-Ridura:SK Beecham). Gold has many mechanisms of action, including inhibition of chemotaxis of inflammatory cells, decreased antibody production (slowly...weeks), inhibition of activation of complement, and decreased phagocytosis. The dosage of the injectable formulation is 1 mg/kg, intramuscularly weekly for induction, then decreased frequency of injections. Possible adverse effects include cutaneous drug reactions (e.g., erythema multiforme), eosinophilia, and thrombocytopenia. Cyclosporine is a fungal (polypeptide of Tolypocladium inflatum) macrolide that inhibits IL-2 activation among many other actions. It is metabolized in the liver and excreted in the urine. Because of the mechanisms of action, it provides a very rapid clinical response (hours/days). Induction is usually accomplished with 5 mg/kg daily. The dose required can be reduced by adding a cytochrome P-450 enzyme inhibitor (e.g., ketoconazole) or metaclopramide into the regimen. This is helpful because the drug is quite expensive. It has the potential for many side-effects, including gastroenteritis, gingival hyperplasia, papillomatosis, nephrotoxicosis, and secondary infections (all less of a problem when lower doses are used). Tetracycline & Niacinamide (or doxycycline & niacinamide) is a drug combination used for years in human dermatology. Tetracycline suppresses chemotaxis of leukocytes and is synergistic with niacinamide. Niacinamide inhibits IgE-mediated mast cell degranulation and decreases protease release from leukocytes. The advantages of this combination is the safety, which is high (rare to find mild dementia or ataxia with treatment) and low cost. It is not recommended for severe disease....rather is appropriate for mild conditions, such as discoid lupus. The dosages are simple: Tetracycline: dogs < 10 kg: 250 mg, q 8 hours dogs > 10 kg: 500 mg q 8 hours Niacinamide: dogs < 10 kg: 250 mg q 8 hours Dogs > 10 kg: 500 mg q 8 hours The drugs are given at this dose until remission or until maximum benefit is seen (30-60 days), then doses can be decreased (e.g., go to q 12 hours for 30-60 days, etc.). This is an outstanding combination for cutaneous lupus erythematosus (DLE) and other mild autoimmune disorders. Doxycycline (5-10 mg/kg) can be used in lieu of tetracycline on a twice daily dosing schedule. Tacrolimus (Protopic7-Fujisama) is a compound with similar actions as cyclosporine (inhibition of IL-2 through inhibition of calcineurin). It is commercially available as a topical ointment (0.1%). Though expensive (~$60.00 per tube), it is used sparingly, so it goes a long way. Tacrolimus is applied twice daily for induction, then in decreasing frequencies for maintenance. Recently, there has been an FDA advisory issued about increased cancer in humans using Protopic over a long-term period of time. It is prudent to advise pet owners to wear gloves when applying this agent. Treatment Schedules Combinations of drugs allow for more rapid response, lower individual drug doses, fewer side-effects, and tend to be more successful in controlling autoimmune skin disease. In dog, azathioprine & prednisone are preferred for induction of MOST autoimmune skin diseases. In cats, chlorambucil & prednisone are preferred for induction. Dosages as previously mentioned are used. We break down therapy into the induction period and maintenance period. Induction is achieved when all old lesions are healed, with the exception of alopecia, and no new lesions are developing. At that time, the doses are slowly reduced during the maintenance period...perhaps more appropriately called the tapering-off period. Patients are monitored during induction with a CBC and platelet count every 7 - 10 days. In addition, a fecal floatation for endoparasites, also controlled by the immune system, should be done every 2-4 weeks. During the maintenance period, a CBC, platelet count, and fecal examination should be performed every 2-4 months. It is also wise to monitor the patient with a biochemistry profile and urinalysis every 2-4 months. A typical schedule for a dog is as follows: 1. INDUCTION Prednisone @ 2.2 mg/kg daily and Azathioprine @ 1-2 mg/kg daily
Induction is defined as the time at which all old lesions are healed and no new lesions are developing. It is wise to wait for 10-14 days after lesions are healed to be reasonably sure that new lesions will not develop…to indicate that induction has been achieved. Comment: Once induction has been achieved, switch one drug to alternate day therapy: leave the other on daily therapy. The decision which drug to switch to alternate day therapy initially, is based on the animals response to the drugs, and adverse effects (i.e., change the drug with the most severe side-effects…first!). 2. FIRST ADJUSTMENT (assuming we choose to reduce the glucocorticoid first) Prednisone @ 2.2 mg/kg every other day and Azathioprine @ 1-2 mg/kg daily
Comment: The net result of this switch for that drug chosen, is a reduction of total dose of that drug by 50% ! Then.....after 2-4 weeks, if there are no new lesions, change the 2nd drug to alternate day therapy. 3. SECOND ADJUSTMENT Prednisone @ 2.2 mg/kg every other day and Azathioprine @ 1-2 mg/kg every other day
Comments: The net result of this adjustment is that both drugs (total drug doses) are now at one-half (50%) of their induction levels. This is a rapid reduction in drugs….and should only be done when the disease is truly in remission. 4. Then, every 2-4 weeks, if there are no new lesions, the dose of one drug can be reduced by 20-25%. Again, we generally work to first lower the dose of the drug that is giving the patient the most problems. Example: if the dog continues to have polydipsia and polyuria…the prednisone would be lowered first…and the azathioprine stay constant. If the white count was lower than desired, we might lower the azathioprine levels, while leaving the prednisone levels at the higher alternate day doses. 5. In most cases, we try to achieve a low-dose, alternate day treatment with prednisone (dogs) or prednisolone (cats) for the longer term maintenance (6-8 months). 6. Many patients will require some low dose maintenance for life, though 25-50% of animals can be taken off medications, IF there are no lesions for 6 months. We target a 6 month disease (i.e., lesion) free time period before attempting to completely discontinue medications. Relapses Relapses do occur as the patient=s doses are decreased. The first step is to make sure that the clinical changes are indeed a relapse of the autoimmune disease. The patient is receiving immunosuppressive therapy, so it is common to see secondary infectious or parasitic (e.g., demodicosis) diseases. A dermatologic data base, consisting of skin scrapings, trichography, impression smears for yeast, and fungal evaluations, should be done when a Arelapse@ has occurred. If the clinical change is determined to be a relapse, options include:
Hypothetical situation: disease recurs when patient is receiving prednisone: 10 mg every other day Pulse schedule: prednisone: 20 (-40) mg daily for 1-2 weeks, then reduce to alternate days (at 20 mg). Comment: The pulse should cause a positive response within one week. If it does not, the patient should be re-evaluated for infections. If there are none, then induction should be re-instituted or new therapeutic agents should be considered. Chemotherapy Safety Many of the drugs given for the management of autoimmune skin diseases are considered as hazardous wastes (e.g., cyclophosphamide) or are inherently dangerous to some individuals. We recommend that all chemotherapeutic drugs be handled only by persons wearing gloves, and that pregnant women, individuals with immunosuppressive diseases or receiving immunosuppressive therapy, children, and the elderly do not give these medications or clean the litter box of cats receiving medications. Medication should be stored in a locked cabinet, out of sight and reach of children, as many of these medications have an appearance resembling candy. The remnants-powder and pieces of tablets left after the vial is empty-should be properly disposed of in a similar manner as chemotherapy waste. Veterinarians have an ethical, legal, and moral obligation to provide adequate information about the safety and possible risks of exposure to these drugs to clients and hospital staff. Summary There are many options when it comes to managing autoimmune skin diseases. The successful program may involve several different drugs in several different protocols. The clinician must be willing to make adjustments as treatment progresses ( or fails). Understanding the mechanisms of these drugs is a strong first step in successful management of patients with these debilitating conditions. Table 1. Treatment Options for Autoimmune Skin Diseases
Managing Pruritus in the Dog: Pathogenesis and Diagnostic Approach Definition: The unpleasant sensation that provokes the desire to scratch, lick, chew, or rub the skin. Note: proper spelling: p-r-u-r-i-t-u-s Pathogenic Factors of Pruritus The sensation of pruritus is transmitted via unmyelinated, c-type nerves that end in the superficial dermis. Irritation of these nerve endings will trigger impulses that are interpreted as pruritus Many substances can irritate the nerve endings, including: preformed mediators of inflammation from mast cells, other proteases (from bacteria and fungi), substance P, various cytokines (leukotirenes, prostaglandins, etc), opiods, and other substances produced by white cells, endothelial cells, and microorganisms. Pruritus may be classified as neurogenic, neuropathic, psychiatric (ie, behavioral), or pruritogenic, the latter which is the type associated with skin disorders. There is spinal antagonism between pain and itch processing neurons, so that itch is essentially under tonic inhibitory control by pain-related signals. This means that the sensation of itch can be ablated by replacing it with pain. That is essentially the mechanism behind scratching to alleviate the itch sensation. Predisposing factors: breed, hair coat, immunocompetency, behavior of the pet, etc Primary factors: allergies, ectoparasites, scaling disorders, neoplasia, autoimmune diseases, psychogenic disturbances, infectious agents, etc. Perpetuating factors: infectious agents (bacteria and fungi such Malassezia spp. yeast), otitis externa, hyperplastic changes of the skin, etc. If we truly want to identify and successfully manage the patient, all three pathologic factors must be addressed. The degree of pruritus shown by a patient is a sum of all the pruritogenic factors. In most patients, there is one (or more) primary factors of pruritus, such as atopic dermatitis. Then, secondary factors, known as flare factors, add to the overall itchiness of the patient and exacerbate the disease. Clinical Manifestations Animals do not demonstrate itching. Itch (pruritus) is the sensation that is felt by the animal. Animals show their "itchiness" by one or more of the following: scratching, chewing (or biting), licking, and rubbing. Pruritus may be so severe as to cause overt pain. Dermatoses associated with pain include: trauma, chemical irritants, toxins, burns and frostbite, ectoparasites, severe infections, neoplasia, and drug eruptions. Overall Philosophy This seems simple. Of course, as Einstein said, "Everything should be made as simple as possible, but not one bit simpler." There is no single "correct" plan to follow which will yield a diagnosis. It may be necessary to utilize all the diagnostic tests available to the veterinarian in order to discover the cause of pruritus in a patient. However, certain keys will help the clinician to isolate the cause or at least to narrow down the possible underlying etiologies of pruritus in each clinical case. These important principles to aid in diagnosis include:
Step 1 : The Initial Visit The Signalment is an important consideration. The age of the patient is used to prioritize possible causes of the pruritus. Obviously some breeds are more predisposed to specific pruritic conditions, such as the Golden retriever and atopy, or the American cocker spaniel and familial seborrhea. The History should include the age at onset of the problem, the progression of the disease, the severity of the pruritus, and the response to any home or veterinary therapy. As always, the history should include the past medical history, environmental history and history of organ systems other than the skin. The Physical Examination is a critical diagnostic procedure! A complete and thorough examination is warranted. It is at this time that the clinician looks to confirm the historical perspective of the client (and referring veterinarian) and recognizes other lesions or patterns previously not noted. Keys include any pattern of pruritus or alopecia, evidence of the severity of pruritus (saliva stains, broken hairs, etc.) or evidence of any systemic disease process. Step 2 : The Dermatology Data Base The data base tests are always performed….in every case….at every visit. Failure to do these tests will dramatically reduce your ability to diagnose perpetuating causes of pruritus and will lead to mistakes.
Step 3: Manage Perpetuating Factors This is the time when all perpetuating factors are controlled: the yeast infections treated appropriately, the bacterial infections controlled with appropriate systemic and topical therapy, and any other "secondary" issues are controlled. A complete integrated flea control program is recommended at this time, even if there is no clear evidence of flea infestation, for those in heavy flea burden areas. If there are NO perpetuating factors found (which is very unusual) then we proceed to step 4. Step 4 : The Recheck Examination Most dermatology cases have numerous perpetuating factors, such as yeast infections and pyoderma. These conditions are treated appropriately, then the patient is re-examined by the same clinician (an important point). Three important things happen at the recheck examination:
Other diagnostics, such as allergy testing, dietary trials, fecal flotation, and cytology (especially ears), and biopsy, may be performed according to "new" information received / "extracted" at the recheck examination. See the TABLE at the end for specific indication of the various diagnostics that may be done at this time. Isolation of the patient in a veterinary hospital or boarding facility may help to determine if the pruritus is due to a substance in the patient's local environment. The reality is that the majority of our pruritic patients are allergic in nature. Therefore, allergy testing, of some type, is the most common diagnostic procedure that will be indicted at this time in the case management. Some tips: 1) TIMING IS EVERYTHING If the pruritus is non-seasonal, and an allergy, either dietary or atopic, is suspected. There are two options: 1) allergy test and if negative proceed with a dietary trial (my preferred choice) OR 2) begin a dietary trial and allergy test if the trial is negative. The main disadvantage of the second option is that it may take 12 weeks to see the full effect of a diet change. Therefore, it would be necessary to control all perpetuating problems for that full 12 weeks while you wait to see if the patient improves. 2) CLIENT EDUCATION is important. We tend to "play the odds" when it comes to performing diagnostic tests. That is, we first recommend the tests that are more likely to yield positive information, then move on to diagnostics that aren't as sensitive or that are more specific for uncommon problems. Remember, most pruritic patients do not have bizarre diseases, they are more likely to have an unusual manifestation of a common disease, such as atopy. Summary The diagnostic approach to pruritus is designed to eliminate those perpetuating factors, such as yeast and bacteria, that complicate the ability to diagnose and manage pruritic skin conditions. Once those perpetuating factors are controlled, the clinical picture bcomes significantly less cloudy and distorted. That does NOT mean that it is always easy to diagnose the primary cause of pruritus. However, following this plan will allow you to practice medicine in a more efficient and purposed manner. Remember…..deal with the "what" (the perpetuating factors), then look for the "why"! Diagnostic Procedures Commonly Used to Evaluate Pruritus
* If appropriate (e.g., pustules, papules)primary or secondary lesions are present. Managing Pruritus in the Dog: Therapeutic Options Introduction There are many therapeutic options that assist in managing pruritus in dogs by controlling perpetuating factors, such as yeast and bacteria, or by reducing inflammation. This discussion will focus on symptomatic management of pruritus due to any cause, but of course, since most of our itchy patients are allergic in nature, the topic does apply primarily to allergic dogs. Topical Symptomatic Therapy of Pruritus Indications for topical therapy: 1) As sole therapy for patients with mild pruritus; 2) As adjunctive therapy with systemic agents described below (Clients are encouraged to use the topical agent during "flare-ups" of the pruritus, which are common in atopic patients.) ; 3) To reduce pruritus during withdrawal periods for systemic anti-inflammatory agents (patients preparing to undergo allergy testing).
Severe pruritus is defined as pruritus so intense that the patient is constantly scratching, licking, chewing, or rubbing the skin. Most patients with pruritus can be distracted from their discomfort. Severe pruritus may result from a combination of pruritic skin disorders or any of the following: 1) scabies (occasionally cheyletiellosis), 2) flea allergy dermatitis, 3) Malassezia dermatitis, or 4) familial seborrhea (probably a summation pruritus). A good clinical history, a thorough dermatologic examination, and the dermatology data base will generally provide all the information necessary to identify the cause of severe pruritus. Scabies is the most challenging of the conditions mentioned above, and it is often necessary, and very appropriate, to treat for this condition (see below) as a Adiagnostic therapeutic trial@. The key is to make certain to re-examine the patient to confirm a positive (or negative) response to the treatment. Do not rely on telephone conversations. Personal experience suggests that your personal examination, and repeat of the data base, is necessary to get a true picture of the patient=s progress. Diagnostic Clues of the Conditions that Cause Severe Pruritus Sarcoptic Mange: Clues include progressive pruritus, worsening with time, multiple animals with pruritus in the household, history of possible exposure, humans in the house with skin lesions, and partial or temporary response to glucocorticoid therapy. Diagnosis is confirmed by skin scrapings, mites in fecal flotations, or by response to therapy. Treatment is easily accomplished with avermectins and a variety of topical acaricides. Malassezia Dermatitis: Clues include a history consistent with atopic disease, malodor, partial or decreasing response to glucocorticoid therapy, greasy skin, relapse of Aatopic signs@, and progressive alopecia & lichenification of the skin. Diagnosis is confirmed with scrapings or impressions of the skin. Treatment is accomplished with topical anti-yeast medications (e.g., Malaseb-DVM) three times weekly, and in severe cases or cases with concurrent otitis externa, ketoconazole at 5-10 mg/kg daily for 21-30 days. Flea Allergy Dermatitis (Flea Bite Hypersensitivity): Clues include a history of flea problems, the presence of fleas or flea dirt, and the classical caudal distribution of lesions. Diagnosis is largely based on the classical lesions and severity of pruritus, though allergy testing may help confirm an allergic tendency in some animals. Treatment is accomplished with an integrated flea control program, usually consisting of topical adulticidal agents, insect growth regulators, and environmental cleaning and control. Familial Seborrhea: Clues include a breed with this tendency (e.g., American cocker spaniel), a recurring history of dermatitis and otitis, and classical lesions including crusts, erythema, ventral neck involvement, lichenification, and otitis externa. Diagnosis is based on the clinical features and ruling out similar and concurrent conditions, such as atopic dermatitis and adverse food reactions. Dermatohistopathology shows parakeratosis at the follicular opening, superficial perivascular dermatitis, and hyperplastic changes. Treatment includes control of secondary bacterial dermatitis, secondary Malassezia involvement, management of the otitis externa and proliferative otic changes. Primary management of familial seborrhea includes use of agents formulated to reduce epithelial turnover (topical tars and systemic retinoids). Miscellaneous: Pruritus is felt to be a cumulative phenomenon. Individual conditions that cause pruritus may be summative....lead to fairly intense discomfort when several conditions, that are not considered intensely itchy, are present. Most often these involve bacterial dermatitis, allergic conditions, secondary cutaneous changes (e.g., dehydration), and other infections (e.g., mild yeast infections). These conditions are easily managed after they are identified with the dermatology data base and an organized diagnostic evaluation. Localized intense pruritus: Several dermatologic conditions may cause severe pruritus at a single location or lesion. These include acute moist dermatitis, acral lick dermatitis, calcinosis cutis. Therapeutic Approach to the Severely Pruritic Dog
References available upon request. |
