Abstract
A previously healthy five-year-old boy was seen in the rheumatology clinic with a five-month history of migrating joint discomfort, followed by right knee and left ankle arthritis. He showed no signs of lymphadenopathy, organomegaly, rashes, or fever. He could not bear weight and had nocturnal pain that was out of proportion to juvenile idiopathic arthritis. Blood tests revealed no pancytopenia. Whole-body magnetic resonance imaging showed extensive enhancement in nearly all bones, suggestive of chronic recurrent multifocal osteomyelitis. However, bone biopsy followed by marrow aspiration confirmed a diagnosis of pre-B-cell leukemia. This case highlights the importance of considering the possibility of childhood malignancies mimicking juvenile idiopathic arthritis and chronic recurrent multifocal osteomyelitis, even in the absence of typical neoplasm symptoms.