COMP and Schmid metaphyseal chondrodysplasia: Matrilin-3 and multiple epiphyseal dysplasia. Similar to MCDS, those forms of MED caused byMATN3 mutations (MATN3-MED) have ER stress and classic UPR as a core disease mechanism19; however, unlike MCDS, cell and mouse models ofMATN3-MED do not respond to CBZ treatment (unpublished data).