Atopic Dermatitis

Description

Atopic dermatitis is a heritable disorder in which animals are hypersenstive to common environmental allergens. It is one of the most common skin diseases of dogs worldwide.

Signalment

Atopic dermatitis is a disease of dogs, although it can occur sporadically in the cat. The typical age of onset of atopic dermatitis is between 6 months and 3 years of age and signs are hardly ever seen in animals under 6 months of age. Atopy is heritable and so breed predispoitions occur. Susceptible breeds include the : Beaceron, Boston Terrier, Boxer, Cairn Terrier, Cocker Spaniel, Dalmation, English Bulldog, English Setter, Fox Terrier, Sealyham Terrier, Setters, Shar-Pei, West Highland White Terrier, Wire Hiared fox Terrier, and Yorkshire Terrier^beale. Certain breeds such as the Cocker Spaniel, Dachshund, Doberman Pinscher, German Shepherd, German Short-haired Pointer and Poodle appear to have a decreased risk of atopy. There is no sex predilection.

Diagnosis

The diagnosis is based on the signalment, a thorough history, appropriate physical examination findings, and ruling out of other causes of pruritus. Differential diagnoses include food allergy (nonseasonal), flea allergy (seasonal), contact allergy, and scabies. The primary reason for pursuing intradermal or serologic allergy testing is to identify the offending allergens in an animal, and to formulate specific immunotherapy. Allergy testing (intradermal or serologic) is a diagnostic aid that measures elevated levels of tissue-bound or circulating IgE; alone, it is not sufficient to diagnose atopy. Test results are significant only if the offending allergens identified are compatible with the history or seasonality of pruritus.

Clinical Signs

Signs are often, but not always, seasonal. Pruritus is the hallmark of atopic dermatitis and may be the only complaint. This gives rise to self-trauma, causing lesions. Lesions commonly include alopecia, erythema, scaling, crusting, excoriations and salivary staining. Macular-papular eruptions are occasionally seen^beale. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption^beale, it follows that hairless regions are most frequently affected: the face, ears, axillae, feet and inguinal regions are predilection sites. Secondary infections such as superficial staphylococcal pyoderma and Malassezia are common, and otitis externa often occurs concurrently^{merck, beale, willemse}. A small number of cases exhibit only chronic or recurrent otitis externa. Another uncommon presentation is allergic rhinitis, manifesting as sneezing, nasal discharge or allergic conjunctivitis^beale.

Treatment

cyclosporin

References

1. Beale, K M (2006) Atopic Dermatitis: Clinical Signs and Diagnosis. Proceedings of the North American Veterinary Conference 2006.
2. Merck & Co (2008) The Merck Veterianry Manual (Eight Edition), Merial.
3. Willemse, T (2007) The Newest on Canine Atopic Dermatitis. Proceedings of the Southern European Veterinary Conference & Congreso Nacional AVEPA.