Blastomycosis of the forearm synovium in a child.

Blastomyces is a pathogen that may infect healthy and immunocompromised hosts. Frequently entering the lungs, the initial pneumonitis usually is followed by skin and bony involvement secondary to hematogenous spread. Infection of the synovium without bone or skin involvement in the pediatric population has not been reported previously. A soft tissue mass of the forearm in a 9-year-old boy was the initial manifestation of blastomycosis. Radiographic images, ultrasound, and magnetic resonance imaging of the forearm could not distinguish inflammation from sarcoma. Frozen section during open biopsy revealed a granulomatous process and several budding yeasts. There was no evidence of a malignancy. Cultures of the tissue grew Blastomyces dermatitidis. The patient was treated successfully with surgical debridement of the mass and amphotericin B followed by itraconazole, for a total therapeutic course of 18 weeks. Although rarely diagnosed in children, blastomycosis must be included in the differential diagnosis of any soft tissue mass.