Steroid-responsive subacute polymyositis in an adult following respiratory syncytial virus infection.

The role of viral infections in the aetiopathogenesis of polymyositis remains speculative. We report a case of profound subacute polymyositis with incipient ventilatory failure following serologically confirmed infection by respiratory syncytial virus (RSV), with a dramatic and sustained response to pulse corticosteroid therapy. We suggest a possible autoimmune mechanism to account for this sequence of events.