Multiple Epiphyseal Dysplasia

Description: This is relatively common disorder of bone and cartilage development that results in delayed appearance of epiphyses, short stature and early onset degenerative arthritis. There are 2 types of MED, which is usually autosomal dominant but can be recessive. The more severe form (Fairbank type or type I) is caused by an abnormality in a protein called ‘cartilage oligomeric matrix protein’ or COMP. The defective gene has been identified in Chromosome 19. Type II or Ribbing type, is a less severe form and abnormal protein is the alpha-2 polypeptide chain of collagen IX (genetic defect in chromosome 1). Type IX collagen is found on the surface of type II collagen and is necessary for the integrity of articular cartilage. There is a defect in the formation of epiphyseal ossification centers. The bones most commonly affected are the humeral (arm bone) and femoral (thigh bone) heads. Bones of the pelvis, spinal column and skull are normal