These pathomolecular mechanisms are particularly relevant to those GSDs that have a significant epiphyseal involvement, such as PSACH-MED, DTDST and the type II collagenopathies, but are perhaps not so relevant for metaphyseal chondrodysplasias such at MCDS where the pathology involves only non-proliferating hypertrophic chondrocytes [16]. Here, COMP is linked to type 2 collagenopathy.