Acute arthritis of the hip in a child infected with the Lyme spirochete.

Acute Lyme arthritis may mimic acute pyogenic arthritis. Although the arthritis associated with infection with the spirochete, Borrelia burgdorferi, is more commonly seen in the chronic stage (Stage III) of the disease, occasionally it may present as the initial clinical manifestation. A five-year-old girl with acute arthritis of the hip is reported to discuss classification and management of arthritis associated with Lyme disease.