As a major component of hypertrophic zone, type X collagen influences deposition of other matrix molecules to this region and thereby provide a proper environment for hematopoiesis, mineralization and modeling that are essential for endochondral ossification.4,5 Mutations and abnormal expression of COL10A1 are closely linked to abnormal chondrocyte hypertrophy that has been seen in multiple skeletal dysplasia and osteoarthritis.6, 7, 8, 9, 10, 11, 12, 13, 14, 15 Schmid metaphyseal chondrodysplasia (SMCD) is an autosomal dominantly inherited skeletal disorder caused by human COL10A1 mutation. The gene discussed is COL10A1; the disease is Schmid metaphyseal chondrodysplasia.