An otherwise healthy 9-year-old girl developed a fever and atraumatic right hip pain with inability to bear weight and exquisite pain with any motion. Her peripheral white blood-cell count was 9.85 × 103/μL, erythrocyte sedimentation rate was 18 mm/hr, and C-reactive protein level was 7.56 mg/L. Aspiration yielded bloody fluid with 611,932 red blood cells/μL, 49,529 white blood cells/μL (92% neutrophils), negative Gram stain, and no crystals. Magnetic resonance imaging revealed an intracapsular lesion anterior to the femoral neck. The joint was irrigated and the lesion was excised. Microscopic examination showed neutrophils interspersed within an otherwise histologically classic tenosynovial giant cell tumor.Conclusion:
Tenosynovial giant cell tumor may rarely present as an acutely irritable hip.