Genetic disorders of connective tissues.

Due to the growing knowledge of structure and function of extracellular matrix proteins, congenital abnormalities of connective tissues are identified or suspected in an increasing number of clinical disorders. In osteogenesis imperfecta and two subtypes of Ehlers-Danlos syndrome, the affected matrix proteins were identified and mutations in the corresponding genes (procollagen type I and type III, respectively) could be demonstrated. Some forms of chondrodysplasia were shown to be associated with mutations in the gene encoding for the cartilage-specific collagen (type II). In part, the clinical phenotype is determined by the tissue-specific distribution of these collagens. However, the correlation of location and character of the mutation to the phenotype is only just emerging and remains unpredictable in most cases. Recent findings suggest the mutations in matrix genes may be causative not only for rare pediatric diseases but also for more common disorders such as osteoarthritis or aortic aneurysms.