HSPG2 and chondrodysplasia: Mutations in the perlecan gene (HSPG2) have been identified in patients with Schwartz–Jampel syndrome, a nonlethal condition characterized by myotonia and mild chondrodysplasia (Nicole et al. 2000; Arikawa‐Hirasawa et al. 2002; Stum et al. 2006).