Erythema Multiforme
Erythema multiforme (EM) is an uncommon syndrome that presumably is immune-mediated. Most cases are unknown in origin but some cases are associated with adverse skin drug reactions, infections, or internal disorders such as connective tissue disease or tumors. The process is associated with keratinocyte cell death, known as apoptosis.
Signs
The skin eruption is usually acute, and often involves the limbs, mouth, armpits, and ears. Signs include red spots on the skin (erythematous macules), pimples (papules), itchy plaques, small and large blisters, erosions, and ulcerations. Crusting and skin discharge are secondary manifestations.
Diagnosis & Treatment
Diagnosis is based on history, clinical signs and laboratory findings. The condition is usually difficult to differentiate from lupus erythematosus and ulcerative dermatosis.
The most common underlying causes are infections (e.g., staphylococcal folliculitis, and anal gland sacculitis, bacterial endocarditis), drugs (e.g., chloramphenicol, cephalexin, diethylcarbamazine, trimethoprim-sulfonamides, etc.), and cancers (e.g., bone disorders, splenic tumors). According to recent changes in the disease classification and identification, erythema multiforme is suspected if patchy lesions with ulcerations are present on less than 10% of the body surface and with more than one mucous membranes affected.
Most cases in dogs have been secondary to bacterial folliculitis or reactions to drugs. If the causative condition can be treated, the disease can be expected to regress spontaneously. Anti-inflammatory doses of prednisolone (0.5 to 1.0 mg/kg/day) may be given to decrease the inflammation and itch when present but are controversial because they can also aggravate some cases. Pentoxifylline has been used occasionally, at 5 to 10 mg/kg 3 times a day, with variable results in recurrent, non-drug associated cases. Azathioprine, sulfasalazine and cyclosporine have also been used as treatments in resistant cases.
- Nesbitt G.E. & Ackerman L.J. Canine Immune-Mediated Skin Diseases. In: Canine and Feline Dermatology: Diagnosis and Treatment. Veterinary Learning Systems, Trenton, New Jersey
- Cutaneous Drug Reactions, Craig K. Svensson, Edward W. Cowen, and Anthony A. Gaspari
Pharmacol
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