Cervical kyphosis: A predominant feature of patients with osteogenesis imperfecta type 5

OBJECTIVES: Osteogenesis imperfecta (OI) is a heterogeneous group of genetic disorders of connective tissue that cause skeletal fragility and extra-skeletal manifestations. Classically, four different types of OI were distinguished. Type 5 OI was added due to its distinct clinical and radiographic features. In 2012, two independent groups identified a recurrent heterozygous c.-14C>T mutation in IFITM5 as the responsible genetic change for this type of OI. To our knowledge, cervical kyphosis has not been identified in the literature as a finding in type 5 OI patients. This is a retrospective review of a cohort of patients with type 5 OI and a description of associated cervical spine deformity. METHODS: After institutional review board approval, a retrospective review identified 13 patients with type 5 OI. Clinical, radiologic, and genetic data from 2002 to 2020 were reviewed. RESULTS: We identified 13 patients with clinical diagnosis of type 5 OI. Twelve had molecular confirmation and the classic IFITM5, c.14C>T gene mutation was identified. The remaining individual did not undergo genetic testing. Dentinogenesis imperfecta was observed in one patient, while blue sclerae or hearing loss were not present. All patients had at least one fracture and four underwent intramedullary rodding. Radiologic features included subphyseal metaphyseal radiodense line in 12/13 patients (92%), interosseous membrane calcification in seven of 13 patients (54%) (more commonly noted in the upper extremities), and hypertrophic callus in six of 13 patients (46%). Thoracolumbar spinal deformities were seen in six of 13 patients (46%) with two of these individuals requiring surgery. Cervical kyphosis was noted in nine of 13 individuals (69%) ranging in age from 3 months to 22 years. Anterior wedging of the cervical vertebral bodies was noted in the absence of any fractures. Six of nine individuals demonstrated listhesis of C2-C3 or C3-C4 segment. Magnetic resonance imaging studies were performed and reviewed in patients with cervical kyphosis and subluxation; three patients showed narrowing of spinal canal without cervical cord compression and one asymptomatic patient showed impingement of the spinal cord. CONCLUSIONS: Cervical kyphosis appears to be a common feature of type 5 OI. It can be a presenting and apparently life-long association and does not appear to be caused by vertebral body fractures. Evaluation for cervical kyphosis should be performed in patients with a suspected or confirmed diagnosis of type 5 OI. Furthermore, if cervical kyphosis is noted in an individual with OI, type 5 OI should be considered. Level of evidence: IV.