Chronic Recurrent Osteomyelitis with Systemic Juvenile Idiopathic Arthritis

A 14-year-old-boy presented with pain and a lump on his left lower leg. Magnetic resonance imaging (MRI) revealed a medullary lesions on T1-weighted images and medullary enhancement after contrast injection. Bone marrow biopsy with curettage revealed an active marrow without evidence of malignancy or infection. The patient had acne on his face and legs. Accordingly, he was diagnosed with chronic recurrent multiple osteomyelitis (CRMO) syndrome. A few months later, the patient developed shoulder joint pain, remittent fever, and an erythematous rash accompanied by a high fever. Blood tests revealed elevated levels of CRP (10.2 mg/dL) and ferritin (557 ng/mL), and hypoalbuminemia (2.8 g/dL). A second bone marrow biopsy revealed hemophagocytosis, but no malignancies. Subsequently, a diagnosis of systemic juvenile idiopathic arthritis (s-JIA) was established.