Pyogenic arthritis complicating varicella infection. 
Arthritis has not previously been reported as a complication in adult patients with chickenpox.  In pediatric patients, the arthritis that complicates chickenpox is most commonly aseptic but does rarely result from bacterial infection.  We report the case of a 21-year-old man who developed acute monoarticular septic arthritis due to Lancefield Group A beta-hemolytic streptococci.  Despite the more common viral cause of arthritis in pediatric patients, physicians should not attribute arthritis associated with varicella in adults to a viral cause without diagnostic arthrocentesis.