Mutations of matrilin-3 have been reported in a variety of skeletal diseases, including multiple epiphyseal dysplasia which is characterized by irregular ossification of the epiphyses and early-onset osteoarthritis, spondylo-epi-metaphyseal dysplasia, and idiopathic hand osteoarthritis [27, 31, 41–49]. The gene discussed is MATN3; the disease is X-linked spondyloepimetaphyseal dysplasia.