Approach To Atopic Dermatitis Student Notes PDF

Slide 1 Approach to atopic dermatitis Shona McIntyre BVMS MRCVS Slide 2 Learning Objectives Define the term atopic dermatitis Be able to identify pathogenesis, causes and clinical signs of atopic dermatitis Describe di...

Slide 1 Approach to atopic dermatitis Shona McIntyre BVMS MRCVS Slide 2 Learning Objectives Define the term atopic dermatitis Be able to identify pathogenesis, causes and clinical signs of atopic dermatitis Describe diagnostic procedures to determine a diagnosis of atopic dermatitis Discuss approaches to treatment and management of atopic dermatitis #universityofsurrey 2 Slide 3 There are three main causes of allergic skin disease in dogs Flea Food ATOPY allergic allergy dermatitis 20-30% of dogs with adverse food reactions have concurrent environmental allergies! #universityofsurrey 3 Slide 4 What is Atopic Dermatitis (AD)? “ A genetically predisposed inflammatory and pruritic allergic skin disease with characteristic clinical features associated with IgE, most commonly directed against environmental allergens ” Muller and Kirk Small animal dermatology Impaired barrier function IgE mediated hypersensitivity reaction Environmental allergens involved in pathogenesis – 80% dogs have specific IgE to house dust mite, grass and other allergens. Atopic-Like Dermatitis: no detectable IgE #universityofsurrey 4 Pathogenesis of Atopic Dermatitis - Not clearly understood - Multifactorial disease with a complex interaction between host and environment - Combination of epidermal lipid barrier defect / IgE mediated hypersensitivity Atopic like dermatitis - No IgE hypersensitivity - An inflammatory and pruritic skin disease with clinical features identical to those seen in canine Atopic Dermatitis in which an IgE response to environmental or other allergens cannot be documented Slide 5 Which dogs get AD? Genetic component but no single gene identified Breed predisposition WHWT, Shar-pei, Boston terrier, Cocker spaniel, Pug Age of onset 5 months – 5 years What about cats? Feline allergic skin disease (FASD) Role of IgE uncertain Combination of genetics and external stimuli Ref: Buckley,L. (2017) Treatment of presumed allergic skin disease in cats. In Practice 39, 242-254 #universityofsurrey 5 What about cats - We don’t call it atopic dermatitis as role IgE unclear - Still get a pattern of cutaneous inflammation and a hypersensitivity dermatitis - Is similar to dogs and associated with genetic predisposing factors and external stimuli - Triggers include flea saliva, food and environmental allergens Slide 6 History General history Dermatological Medical history history Management In contacts Diet Environment #universityofsurrey 6 - Generally history - has owner always had dog, do they know its history? Does it have GIT signs that might indicate a food problem? Remember most atopic dogs systemically well - Medical - any other conditions which might be related? Endocrine dx? Any concurrent medicationss which might affect skin conditions - In contacts - any people or animals affected? - Environment - is the animal sleeping in the bed where there is a high concentration of dust mites. Where are they exercised? Might affect parasites and pollens exposed to. Do they swim as this will affect parasite control - Diet - can owners do an accurate diet history, important for diet trial - Management - what is flea control? Do they treat all animals in house? How often do they bath the animal and with what? - Dermatological history - when did they first see signs and what were they (relevant as atopic dogs often show signs between 5m and 5y) - Is problem continuous/seasonal? - Where did the lesions start on the animal. Secondary infections might affect the pattern distribution of lesions - Get owners to grade pruritus – use visual scale - Think about previous treatments and tests, has anything helped in the past? Slide 7 Clinical Signs Pruritus Erythema Saliva staining Recurrent otitis Pyoderma Pododermatitis Malassezia dermatitis Excoriation, lichenification and alopecia (chronically) #universityofsurrey Barnard,N.(2020) A clinicians guide to marking a diagnosis of atopic dermatitis in dogs. In Practice 42, 188-196 7 Slide 8 Clinical Signs Small animal dermatology a colour atlas and therapeutic guide. Hnilica;Medleau 2011 #universityofsurrey 8 Pictures: 1. Alopecia with erythema and hyperpigmentation on the ventrum of an atopic dog, demonstrating typical lesion distribution for atopy. Note the similarity in distribution with Malassezia dermatitis. 2. The periocular alopecia and hyperpigmentation caused by facial pruritus are typical of allergic disease. 3. Pododermatitis with alopecia and erythema affecting the interdigital tissue between the central pad and digits. Pododermatitis and foot pruritus are some of the most consistent findings of atopy. 4. Erythema and lichenification of the ear canal associated with secondary yeast otitis. Otitis is a common finding in allergic dogs. 5. Secondary Malassezia dermatitis caused by underlying allergy. The alopecic, erythematous, lichenified lesion on the ventral neck of this allergic dog is typical of Malassezia dermatitis. 6. Severe erythema of the feet caused by intense pruritus and by the patient self-mutilating his feet. Leading to pododermatitis Slide 9 Lesion distribution #universityofsurrey Hensel et al. BMC Veterinary Research (2015) 11:196 9 Breed specific variations of lesion distribution do occur French Bulldogs – eyelids, flexor surface of joints GSD – elbow, hindlimb, thorax Sharpei – thorax, dorsolumbar area Boxer - ears Slide 10 Important differentials Pruritus is a ‘PAIN’ Parasites Fleas Harvest mites Sarcoptic mange Cheyletiellosis Demodicosis Lice Otodectes Allergy / Autoimmune Flea allergy Atopic dermatitis Cutaneous adverse Contact Allergy food reaction (CAFR) Pemphigus folliaceus Infection Bacterial pyoderma Malassezia dermatitis Dermatophytosis Neoplastic/Neurogenic Cutaneous lymphoma Feline orofacial pain Feline psychogenic syndrome alopecia Acral lick dermatitis #universityofsurrey 10 Slide 11 Diagnostic investigation Steps in reaching a diagnosis of Atopic dermatitis 1. Are history and clinical signs suggestive of a diagnosis? 2. Have ectoparasites been ruled out? 3. Has infection been ruled out? 4. Has food been ruled out? #universityofsurrey 11 Slide 12 Atopic Dermatitis Diagnostic Criteria Onset < 3years old Dog living mostly indoors Glucocorticoid responsive pruritus Alesional pruritus at onset Affected front feet Affected ear pinna Unaffected ear margins Unaffected dorsolumbar area Favrot et al (2010) Veterinary Dermatology 21, 23-30 #universityofsurrey 12 These criteria were published to aid diagnosis. But there is still 20% misdiagnosis if we apply these strictly. So need to ensure we have ruled out ectoparasites and skin infections before we apply this as a diagnostic aid Ideally looking for a patient to satisfy 5 criteria giving an 85% sensitivity and 79% specificity Slide 13 Rule out ectoparasites Coat brushing → flea dirt /cheyletiella Hair plucks → hair structure Skin scrapes → Demodex / Sarcoptes Sarcoptes IgG serology Otoscopic examination → Otodectes cynotis Trial treatment → flea treatment / sarcoptic mange #universityofsurrey 13 Slide 14 Rule out infections Pyoderma →Staphylococcus pseudointermedius o Papulopustular eruptions and epidermal collarattes Malassezia dermatitis → Malassezia pachydermatitis o Found in areas of skin folds with lichenification and oily seborrhea How do we rule these out? Tape strip Impression Smear Cytology #universityofsurrey 14 Pruritic patients often have secondary yeast or bacterial infections and these are itchy so these secondary causes should be investigated. Cytology best way to investigate with tape strip, impression smear and ear cytology and can all be done in house with a microscope. Treating theses secondary infections will improve quality of life by reducing pruritus Slide 15 Rule out food Canine Adverse Food Reaction Non seasonal pruritus +/- gastrointestinal signs Diagnosis Diet trial o Novel protein and carbohydrate source o 6-8 weeks o If recurrence following reintroduction of food then positive diagnosis #universityofsurrey 15 CARF also known as food allergy or food hypersensitivity presents as a non seaonsal pruritus very similar to Atopic Dermatitis. Although some animals can also have GIT signs. The only way to diagnose this is with a diet trial with a novel protein and carbohydrate. This should be fed for 6-8 weeks. Success is dependent on owner compliance and accurate dietary history. After this time reintroduce original food and if relapse occurs then CARF diagnosed. This done over a two week period. If relapse put back onto exclusion diet and clinical signs should resolve. Pitfalls - Feeding table food/snacks. Hiding medication in food, flavoured toothpaste, using flavoured drugs like worming tablets - Cant even lick another dogs bowl or eat another dogs faeces! Slide 16 You diagnosed atopic dermatitis…. Now what???? #universityofsurrey 16 Slide 17 Allergy Testing Intradermal testing Mast cell reactivity due to presence of IgE Allergens should be chosen appropriate to region Performed on lateral thorax Positive (histamine) and negative (saline) control used for comparison Allergen specific IgE serology Often done on a panel of allergens Variation between tests used Do drugs matter? #universityofsurrey 17 These are screening tests for allergens, not diagnostics. Advantages of serology - No sedation, less traumatic with less injections, more convenient, lower risk of drugs interfering with results. - Can however show positive results in non allergenic dogs and sensitivity not as high as with intradermal testing. Do drugs matter? - antihistamines, glucocorticoids, progesterone products, tricyclic antidepressants and bronchodilators can all interfere with intradermal testing - Ketamine, ACP and diazepam should not be used as a sedative as can interfere with tests. - Standard withdrawl times for drugs have been suggested - Antihistamine 7days, oral prednisolone 14days, parenteral glucocorticoids 28days, topical glucocorticoids 14days Slide 18 Treatment of Atopic dermatitis in dogs Management of flare factors Acute flare up vs Chronic disease Skin and coat care Allergen-specific management Pharmacotherapy Biological therapies #universityofsurrey 18 If there is the need to treat short term pruritus while undertaking the ectoparasitic treatments and food trials then short courses of glucocorticoids can be used, however these must be stopped in order to assess the response to the trial. Once a diagnosis of atopic dermatitis is reached then long term management is instigated. However even within this there is always adjustments to be made. You may be on a stable treatment regime and then the animal has an acute flare up and treatment needs to be adjusted in the short term to get the animal back under control. These flare ups often occur when the animal has reached its pruritic threshold of exposure to an allergen. Slide 19 Acute Flare ups Management of flare factors Skin and coat care Topical or systemic Emollient shampoos antibiotics Lipids, complex sugars, Itraconazole for Malassezia antiseptics Parasite control Frequency and intensity of bathing important Allergen-specific management Topical or systemic antibiotics Itraconazole for Malassezia Parasite control #universityofsurrey 19 Slide 20 Acute Flare ups Management of flare Allergen-specific factors management Pharmacotherapy Topical or systemic antibiotics Allergen avoidance Topical glucocorticoid Itraconazole Consider for Malassezia pollens/house dust SID for 1-2 weeks mites Parasite control Oral glucocorticoids Consider where animal 0.5-1mg/kg SID/BID then taper exercised Oclacitinib 0.4-0.6mg/kg BID for 14d #universityofsurrey 20 Slide 21 Chronic Atopic Dermatitis treatment Management of flare factors Skin and coat care Parasite control Emollient shampoos Use oral/systemic Lipids, complex sugars, House dust mites antiseptics Freeze dry food Bath at least weekly Wash face after eating Essential Fatty Acid Food storage supplements Reconsider diet trials #universityofsurrey 21 Slide 22 Chronic Atopic Dermatitis treatment Allergen Specific Management Allergen specific immunotherapy Subcutaneous injection Sublingual Allergen avoidance #universityofsurrey 22 Allergen specific immunotherapy – injectable or sublingual - Not licenced so needs imported under a special certificate. The injectable allergen make up is based on allergy test results - Success variable - Inject with incremental dose of allergen to reach maintenance of inject every few weeks but process can take 12 months - Often used in conjunction with other therapies and is life long - Safe, owners can give Or can be done sublingually – similar efficacy - this needs administered twice daily long term so need owner commitment - Adverse effects are uncommon but include increased pruritus, lethargy, vomiting, diarrhoea and mild angioedema. Allergen avoidance wont on its own make dog better but may help. - Prevent dust accumulation by removing ‘clutter’ from sleeping areas; for example, toys, chews and excess bedding; - Keep dogs out of the human bedrooms and away from carpeted areas if possible; - Wash bedding regularly (weekly) on a hot cycle; - Reduce the temperature of sleeping areas and increase ventilation; - Vacuum, clean and dust frequently. - Store dry food in plastic container and freeze. Wash dogs face after eating - Washing down feet when come in house Slide 23 Chronic Atopic Dermatitis treatment Pharmacotherapy Glucocorticoids 0.5mg/kg SID/BID Rapid onset action Taper to effective dose and freqeuncy Oclacitinib (Apoquel®) 0.4-0.6mg/kg BID for 14 days then SID Rapid onset action (24-48hrs) Ciclosporin (Atopica®) 5mg/kg SID Slow onset action so combine short term with glucocorticoid #universityofsurrey 23 Slide 24 Chronic Atopic Dermatitis treatment Biological Therapies Cytopoint Monoclonal antibody 1mg/kg subcutaneous injection Every 4-8 weeks #universityofsurrey 24 Cytopoint – In one study 77 per cent of dogs treated had a greater than or equal to 50 per cent reduction in owner-assessed levels of pruritus and clinical improvement was noted within 24 hours in 56 per cent of dogs treated (Souza and others 2018). May reduce the amount of additional drugs required and convenient for owners as monthly injection in clinic. Greater response to treatment than allergy specific immunisation Slide 25 Summary Ensure you have a diagnosis of Atopic Dermatitis by excluding other possible conditions Animals have a pruritic threshold so will have recurrent flare ups Multiple treatments are often required and treatment must be adjusted during flare up episodes #universityofsurrey 25 Slide 26 26