Birth fractures in spinal muscular atrophy.

Three patients with birth fractures and Werdnig-Hoffmann disease are presented. Two of the three were erroneously diagnosed as having osteogenesis imperfecta. The etiology of these fractures appears to be in utero osteoporosis secondary to decreased movement, leading to pathologic fracture during birth. Immobilization led to uneventful healing in all cases; no recurrent fractures were seen.