A previously healthy 3-year-old girl had 3 days of fever, decreased activity, and a limp. There was no antecedent trauma. She reported left hip pain and her mother noted an abnormal gait. On examination, the patient's temperature was 39.2°C. She had bilateral cervical lymphadenopathy with a prominent right-sided 2 × 2-cm anterior cervical lymph node with mild tenderness but no warmth or erythema. At her left hip, there was no tenderness to palpation, but range of motion was limited. The patient's peripheral white blood cell count was 13 400/μL (to convert to ×109/L, multiply by 0.001) with 36% segmented neutrophils. Her erythrocyte sedimentation rate was 72 mm/h, and C-reactive protein concentration was 3.2 mg/dL. Urinalysis, basic chemistry, and hepatic function testing results were within normal limits. Serologic tests for Bartonella henselaeantibodies did not reveal evidence of acute infection (IgM < 1:16; IgG, 1:128).