Clinical features: Osteogenesis imperfecta is a group of inherited conditions characterised by fractures associated with minimal or absent trauma, dentinogenesis imperfecta, (DI :imperfect dentine formation), blue sclerae and in adults, progressive hearing loss. The clinical features of OI are extremely variable and range from perinatal lethality to individuals with severe skeletal alterations, mobility impairments, and very short stature to nearly asymptomatic individuals with a mild predisposition to fractures, normal stature, and normal lifespan. OI is currently classified into seven types. This classification is based on the clinical presentation, X-ray findings, bone morphology and DNA studies and is helpful in providing information about prognosis and management. However, the features of different types of OI overlap considerably and it is not always easy to classify individuals. If possible, patients with OI should be managed by a multidisciplinary team focusing on supportive therapy to minimise fractures and disability and maintain overall health.
Incidence: Considering all types together, OI has a prevalence of approximately 6-7 per 100,000.
Inheritance: Autosomal dominant (types I ? V), the proportion of cases caused by a new mutation varying by the severity of disease. Autosomal recessive (type VII), uncertain (type VI).
Gene: More than 90% of individuals with OI types I ? IV, These genes have not been found to have mutations in type V-VII in one of two genes, COL1A1 (chromosome 17) and COL1A2 (chromosome 7).
Prenatal diagnosis: Possible by DNA testing if mutations identified in affected family members. Detailed fetal ultrasonography at 20 weeks gestation can be valuable in the antenatal diagnosis of the most severe forms of OI. Milder forms may be detected later in pregnancy if fractures or deformities occur, but this is not common. If a family is considering prenatal diagnosis referral should be made to the local clinical genetics service prior to a pregnancy. This ensures family members are offered appropriate advice and investigations, to confirm whether or not prenatal diagnosis is possible.
Brittle Bone Society
30 Guthrie Street
Tel : 08000 282459 (Freephone helpline for advice only)
Tel: 01382 204 446
Fax: 01382 206 771