Rheumatoid bursitis extending into the clavicle and to the skin surface

A woman with rheumatoid arthritis developed persistent sterile drainage from a cutaneous fistula after biopsy of an inflamed supraclavicular mass. Radiographs showed several cavities in the underlying clavicle. Inability to culture a pathogen and failure of the fistula to heal despite empirical courses of antibiotic therapy led to surgical intervention. The final diagnosis, based on careful histological analysis by special staining techniques, was rheumatoid bursitis extending into the clavicle and to the skin surface.