The cervical spine in fibrodysplasia ossificans progressiva.

Radiographs of the cervical spine in 11 patients with fibrodysplasia ossificans progressiva (FOP) have been examined, and abnormalities found in all. In 4, small cervical vertebral bodies with enlarged pedicles were seen in early childhood; later, variable fusion of the vertebrae was apparent in all patients. This fusion was first noted between adjacent neural arches in late childhood but also involved the vertebral bodies in some adult patients. It was only sometimes associated with ossification of the adjacent neck muscles, and appeared to be an important cause of neck stiffness in FOP. The radiological changes may be confused with those of Still's disease or of the Klippel-Feil syndrome.