TYPE-II COLLAGEN MUTATIONS IN RARE AND COMMON CARTILAGE DISEASES

Cartilage diseases include a wide variety of clinical phenotypes from common osteoarthrosis to several different types of chondrodysplasias, i.e. disorders of cartilage', of which more than 100 different have b een described. Patients frequently suffer from various symptoms affect ing their joints and/or the growth of their long bones. The amount of hyaline cartilage at articular surfaces is often diminished and struct urally abnormal. The surface of the cartilage may have an irregular ap pearance with defects extending into the subchondral bone. The major c onstituents of this hyaline cartilage are collagens and proteoglycans, the most abundant protein being type II collagen. It is a homotrimer of three identical a-chains, which are encoded by a single gene on hum an chromosome 12. The gene for type II collagen therefore became a lik ely candidate for some forms of chondrodysplasias and cartilage degene ration. Recently, both linkages and exclusions between this gene and v arious cartilage diseases have been reported and a growing number of m utations within the gene have also been identified.