The identification of an in-frame deletion/insertion (c.513_530del), which is predicted to result in a p.Asp171_Glu177delinsGlu in the α4 helix, is the first mutation of this kind to be identified in MATN3 and thus extends the type of mutations in MATN3 that can cause MED. The gene discussed is MATN3; the disease is multiple epiphyseal dysplasia.