ZEB1 and keratoconus: Notably, although ZEB1 missense variants typically associate with KC/FECD (vs. truncating mutations in PPCD3), our findings and recent reports (Mazzotta et al., 2014; Bykhovskaya et al., 2016), suggest missense variants may also contribute to PPCD3 pathogenesis, particularly in cases of overlap of KC and PPCD3.