Muscle involvement in a patient with Henoch-Schönlein purpura nephritis.

Although Henoch-Schönlein purpura (HSP) is a small-vessel vasculitis affecting multiple organ systems, muscle involvement has rarely been reported. This report describes muscle pain and weakness in a patient with HSP nephritis (HSPN). A 13-year-old boy suffered from purpura, abdominal pain, and symmetrical muscle pain and weakness of the extremities. He was diagnosed as having HSP with muscle involvement. His abdominal pain and muscle involvement improved 1 week after commencing oral prednisolone therapy. The patient subsequently developed biopsy proven HSPN. It should be noted that, although rare, muscle involvement might occur in HSP as in other systemic vasculitides. The precise pathogenic mechanism underlying its development is currently unclear.