Difference between revisions of "Atopic Dermatitis"

Revision as of 15:26, 26 August 2010

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

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.

Laboratory Tests

Biopsy

Other Tests

Pathology

Treatment

cyclosporin

Prognosis

Links

References

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

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 ===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<sup>beale</sup>. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption<sup>beale</sup>, 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. 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.
+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<sup>beale</sup>. With time, lichenification, and hyperpigmentation develops. Because the route of allergen contact is thought to be percutaneous absorption<sup>beale</sup>, 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<sup>merck, beale, willemse</sup>. 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<sup>beale</sup>.
-In dogs pruritus is considered a hallmark of atopic dermatitis and emphasized by feet licking and nose or head rubbing. Since the occurrence of primary cutaneous lesions has never been firmly established, it may be that all the cutaneous changes are secondary to itch-induced scratching. This hypothesis is supported by the finding that although all of the dogs have signs of face rubbing and feet licking, only two-thirds have cutaneous lesions at the muzzle and pedal areas. In mild cases, one may only see broken hairs or salivary discoloration (rust colored) of the hairs. The incidence of a superficial pyoderma and of Malassezia infection is significantly higher in dogs with atopic signs together with immediate skin test reactivity, than in dogs with clinical manifestations but without a positive skin test. Otitis externa is a common finding in atopic dogs (up to 80 per cent) and even in 40 per cent of dogs as the initial problem. The head and legs are involved in 70 - 80%, and the axillaries, the abdomen and/or groins in 40 - 60% of dogs.
 ===Laboratory Tests===