Sporadic osteogenesis imperfecta type V in an 11-year-old Japanese girl

Abstract

We report a sporadic case of osteogenesis imperfecta (OI) type V with hyperplastic callus (HPC) formation in an 11-year-old Japanese girl. OI, commonly known as brittle bone disease, is a rare connective tissue disorder characterized by bone fragility and low bone mass. At present, OI can be classifi ed into at least eight types, designated types I–VIII, based on clinical features and specifi c gene mutations. OI type V is a rare form that represents 4%–5% of all OI cases and is characterized by HPC. All patients with HPC have OI type V. Increasing evidence suggests that OI type V shows an autosomal-dominant pattern of inheritance with unknown associated mutations. To date in the English-language literature, fewer than 90 OI patients with HPC formation have been reported, including 30 without a familial background of OI. Only three Japanese cases consistent with OI type V have been described in two detailed reports. Each patient had a family history of OI, and no Japanese cases of OI type V without a familial background has previously been documented. To the best of our knowledge, the present report represents the fi rst description of sporadic OI type V in a Japanese patient.