Pseudomonas aeruginosa infection-associated erythema multiforme in a Maltese dog.

An 8-year-old spayed female Maltese dog was referred with a 4-month history of multifocal pruritic erosive or ulcerative lesions on the head, ventral neck, chest, and abdomen; and chronic otitis externa. Biopsy revealed cytotoxic dermatitis and apoptotic keratinocytes with occasional lymphocytic satellitosis. Bacterial culture and antimicrobial susceptibility tests revealed multidrug-resistant Pseudomonas aeruginosa infection of the skin and ears. The skin lesions regressed after treatment of P. aeruginosa infection with ciprofloxacin. Based on the skin lesions, histological characteristics, and response to therapy, the dog was presumed to have erythema multiforme induced by P. aeruginosa infection. This case report emphasizes that P. aeruginosa infection could be a trigger of erythema multiforme in dogs. Key clinical message: Erythema multiforme caused by infection is rare and poorly characterized in the veterinary literature. This case report describes the clinical characteristics of, diagnostic approach to, and treatment of erythema multiforme caused by Pseudomonas aeruginosa.