Rocky Mountain spotted fever presenting with acute monarticular arthritis.

This report describes a 30-year-old man who presented with an acute multisystem illness which was diagnosed as Rocky Mountain spotted fever (RMSF). Near the time of admission the patient was noted to have a newly developed aseptic monarticular arthritis of the right knee. The arthritis resolved in association with resolution of his systemic illness. To our knowledge, there have been no prior reports of acute arthritis in association with RMSF.