Air in bone: intraosseous pneumatocyst in a child

Abstract

Intraosseous pneumatocyst [1] is an uncommon benign condition in which gas collects in bone. The imaging features are of a localized collection of gas in the bone, usually adjacent to a joint, a thin sclerotic rim, no bony destruction, no soft-tissue mass and no other medullary abnormalities. The differential diagnosis for this incidental finding includes osteonecrosis, osteomyelitis, neoplastic or post-traumatic vertebral collapse, and postoperative changes. There may be progression to a fluid-filled cyst. The axial and sagittal CT images (Fig. 1) are of a 9-yearold boy with abdominal pain due to blunt trauma showing well-defined intraosseous air (−940 HU) with a sclerotic margin in the left ilium adjacent to the sacroiliac joint. No fractures or joint abnormality was noted and the appearances are consistent with an intraosseous pneumatocyst. This is a distinct but benign entity [2] and has to be kept in mind, particularly in patients with a history of trauma to avoid unnecessary investigations.