Chronic localized osteomyelitis caused by atypical infection with Blastomyces dermatitidis in a dog

A 4-year-old male Golden Retriever was evaluated because of chronic non-weight-bearing lameness of the right hind limb associated with penetrating tarsal wounds. Arthritis of the tarsal joint and osteomyelitis of the talus were initially evident. Tarsal arthrodesis was performed 7 months after initial injury, but the lameness persisted. Ten months later, blastomycosis was diagnosed on the basis of results of histologic examination of bone biopsy specimens and serologic tests. No other site of involvement was detected. The limb was amputated, and Blastomyces dermatitidis was isolated from the affected bone. Adjuvant antifungal treatment was not given. Ten months after amputation, the dog was in good health, and the antibody titer for B dermatitidis was low, indicating resolution of the infection. Localized bone infection with B dermatitidis is rare in dogs. In this dog, it was believed that blastomycosis was contracted through direct inoculation of the organism, because the lesion was associated with puncture wounds and other sites of involvement were not found.