Clinical and Genetic Classification of Osteogenesis Imperfecta and Epidemiology

Osteogenesis imperfecta is described as a "rare" disorder occurring in approximately 1 per 10,000 live births. Most physicians do not treat individuals with OI, and this may present problems when diagnostic or treatment decisions are required. However, OI is one of the most common of the inherited disorders of connective tissue and is significantly under-diagnosed. The prevalence of OI is not explored in many populations around the world.More than 95% of individuals with OI are heterozygous for mutations in either of the two type I collagen genes, COL1A1 and COL1A2. The discovery of genes associated with recessive inheritance identified the genes in which bi-allelic mutations resulted in recessive inheritance and broadened the clinical classification of OI (types I-IV) proposed by Sillence in 1979. These new discoveries have created a tension between an expanded clinical classification, one based solely on genetic grounds, or some middle ground that adopts some of the clinical elements used for classification (historical) and melds them with the more recent genetic findings.