Synovitis in toxic shock syndrome (TSS) is an unusual finding.A 31-year-old man presented with pain and swelling in both knees and was found to have TSS, secondary to a septic bursitis caused by Staphylococcus aureus. Immune complexes were not detected in serum or synovial fluid, and the S aureus was not recovered from the inflamed joints. Antibodies against the TSS todn-1 were detected in serum and synovial fluid, but in lower levels than would be seen in a normal control serum. Complement studies implicated alternative pathway :activation by a marked diminution in C3 levels compared with C4 levels, and by lower levels of factor B than would be found in other inflammatory joint diseases. The diagnostic dilemma posed by TSS in a man is discussed.Toxic shock syndrome (TSS) following staphylococcal infection was initially associated with menstruation and tampon use, but reports of nonmenstrual TSS :associated with various types of staphylococcal infections have appeared (1). A small number of patients with TSS have been described as having acute synovitis (2,3). However, this finding has not been studied in detail. We describe the clinical features of a patient who developed an aseptic arthritis when he had TSS associated with staphylococcal septic bursitis. The report provides data about possible immunopathogenesis of the synovitis.Case report. A previously healthy 3 I-year-old white man presented to the emergency department with a 3-day history of sore throat, cough, fever, headache, dysuria, severe myalgias, and a rash. Four days prior to admission he had noted a small circular lesion over the right knee. He then experienced increasing difficulty with walking, due to pain and swelling in both knees. Two days prior to his admission, he experienced nausea, vomiting, fever, and chills. He had no history of drug ingestion, penile discharge, dysuria, alcohol abuse, or intravenous drug abuse.Examination revealed an acutely ill male in marked respiratory distress. He was confused, agitated, and disoriented. His pulse rate was 140/minute, blood pressure was 96/20 mm Hg, temperature was 3 9 T , and respiratory rate was 25Iminute. There was diffuse macular erythroderma with areas of central clearing over his trunk, arms, legs and palms. Scattered petechiae were present. Cardiovascular, respiratory, and abdominal examination results were otherwise unremarkable. His pharynx was reddened. He had no oral ulcerations and no conjunctivitis. Musculoskeletal examination revealed redness, warmth, and large effusions in both knees, but no other synovitis was present. There was a 1-cm circular crusted lesion over the right prepatellar bursa, with reddish discoloration in that area.Results of laboratory investigations showed hemoglobin 15.7 gm/dl, white blood cells (WBC) 19.5 x 103/ml, and normal electrolyte values. Urinalysis showed proteinuria (3+), 5-10 WBC, 3-5 epithelial cells, 2+ bacteria. Blood urea nitrogen level was 14.1 mmolesfliter (normal 3-7); creatinine was 237 pmoles/