Mutations in many different ECM protein genes can interfere with this orchestration and disrupt normal skeletal growth.1-3) Among them, cartilage oligomeric matrix protein (COMP) has been identified as the abnormal protein in two types of human autosomal dominant skeletal dysplasias: pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia.4,5) The tissue pathology of the growth plate cartilage is striking in patients with PSACH. The gene discussed is COMP; the disease is pseudoachondroplasia.