Delayed diagnosis of a primary psoas abscess mimicking septic arthritis of the hip.

A 5-year-old boy presented with a limp, fever, and right hip pain of 72 hours' duration. An intensive workup of right hip pain synovitis failed to diagnose any local pathology. Delayed diagnosis of psoas abscess was made on the 12th day of hospitalization. A rapid recovery with no further complications followed surgical evacuation of the abscess.