Osteogenesis imperfecta type V: Genetic and clinical findings in eleven Chinese patients

Osteogenesis imperfecta (OI) type V is a rare inherited disease characterized by multiple fractures, intraosseous membrane calcification, and hypercallus formation. We investigate the causative gene, phenotype and also observe the effects of zoledronic acid in Chinese OI type V patients.

The clinical phenotype and causative gene mutation was investigated in eleven patients with type V OI. Patients were given a dose of zoledronic acid 5mg intravenously. Fracture incidence and Z-score of bone mineral density (BMD) were evaluated. Serum levels of biomarkers such as cross linked C-telopeptide of type I collagen (β-CTX) and safety parameters were assessed.

The c.-14C>T mutation in the 5' untranslated region of IFITM5 was detected in all patients. The phenotype was largely variable, and no significant correlation of genotype and phenotype was found. After one dose of zoledronic acid infusion, fracture incidence significantly dropped from 2fractures/year before treatment to 0fracture/year after treatment (P=0.01). Z score of lumbar spine BMD elevated from -2.6 to -1.3 (P<0.001). Serum β-CTX level decreased by 50% (P<0.05). No serious adverse event was found.

No obvious correlation was found between the genotype and phenotype. Zoledronic acid had significantly skeletal protective effects in OI of type V.