An 11-month-old girl was referred to the Department of Rheumatology and Clinical Immunology at Tianjin Children's Hospital with polyostotic lesions. About 1 month previously, her mother had noticed multiple non-tender sclerotic bulges over the bones of the skull, left upper arm, right forearm, right clavicle, left chest wall, and right pelvis. The patient had no fever and was otherwise healthy. She was initially taken to another hospital, where she underwent an emission CT scan. Bone metastasis was suspected, but malignancy was ruled out after a biopsy was conducted on the frontal bone of the skull.