Hip Pain in an 18-year-old Man

Abstract

An 18-year-old man presented with a 6-month history of left hip pain. There was no antecedent trauma but a gradual onset of pain that became persistent over the 6-month period. The patient’s pain intensified with time and a bothersome limp on the left side was affecting his activity level. He had no other complaints or constitutional symptoms, nor did he report any chest pain or shortness of breath. His medical history was unremarkable. Family medical history was significant for B cell lymphoma in the patient’s maternal grandfather. On physical examination, the patient appeared healthy with stable vital signs and no apparent distress. No regional or distant lymphadenopathy and no soft tissue mass were present around the hip. He was tender to palpation in the left groin and greater trochanter. Range of motion of the hip revealed pain with rotation, greater with external than internal rotation. Flexion and extension did not produce pain. The neurovascular exam was normal, with 2 + dorsalis pedis and posterior tibial pulses. Motor examination was 5/5 and sensation was intact throughout all dermatomes. Laboratory examination revealed an elevated white blood cell count of 12.7 · 10/lL, an elevated sedimentation rate of 21 mm/hour, and an elevated C-reactive protein of 15.4 mg/L. Imaging studies included anteroposterior and lateral radiographs (Fig. 1), radionuclide Tc-99m methylene diphosphonate bone scan (Fig. 2), computed tomography (CT) scan (Fig. 3), and magnetic resonance imaging (MRI) (Fig. 4). Based on the history, physical examination, laboratory studies, and imaging studies, what is the differential diagnosis?