Chronic recurrent multifocal osteomyelitis in a 3.5-year-old boy.

We report an extremely rare case of multifocal bone disorder in a 3.5-year-old boy who appeared for left forearm and arm pain and multiple periods of fever with an unusual presentation of lymphoma/leukemia and highlight diagnostic challenges leading to a misdiagnosis, which was then diagnosed and treated for chronic recurrent multifocal osteomyelitis (CRMO). Based on a left arm biopsy and whole-body scans, he was eventually diagnosed with CRMO.