The variant p.T2436N affects domain IV, which has a major role in PCM stabilization; the variant p.A4328T affects the terminal globular subdomain of domain V and may disrupt cell–integrin adhesion and interactions with vascular endothelial growth factor A. Unlike DDSH and SJS1, however, keratoconus is likely polygenic, where the accumulation of additional genetic defects is responsible for disease penetrance. Here, HSPG2 is linked to keratoconus.