HSPG2 and Silverman-Handmaker type dyssegmental dysplasia: Dyssegmental dysplagia Silvermann–Handmaker type (DDSH), another disease caused by mutations in HSPG2, is characterized by a complete loss of perlecan function and lack of extracellular perlecan expression, whereas SJS is associated with a partial loss of perlecan function and some extracellular expression of perlecan [5].