Pectoralis pyomyositis: an unusual cause of chest wall pain in a patient with diabetes mellitus and rheumatoid arthritis.

We describe a case of isolated pectoralis swelling and tenderness, without systemic signs of infection, in a North American adult with diabetes mellitus and rheumatoid arthritis. The etiology was discovered to be pyomyositis, usually thought to be a disease of tropical climates. It is the first such case with group B Streptococcus as the causative organism.