Clinical screening for collagen defects in connective tissue diseases

The defects in type I collagen structure or synthesis that produce all four types of osteogenesis imperfecta (OI) and Ehlers-Danlos syndrome (EDS) type VII and the defects in type III collagen structure in EDS type IV can be detected by analysis of collagens produced by fibroblastic cells cultured from affected individuals. Quantitative defects in synthesis of type I collagen are seen in OI type I and qualitative defects of type I collagen characterize OI type II, OI type III, and OI type IV and EDS type VII. EDS type IV results from qualitative type III collagen defects. All of the disorders are inherited typically in an autosomal dominant fashion so that recurrence among offspring of normal parents usually results from germline mosaicism for the mutation in one parent. Analysis of type I and type III collagen synthesized by cultured chorionic villus cells is used for prenatal diagnosis of these disorders.