In 2 affected members of a family with posterior polymorphous corneal dystrophy, Biswas et al. (2001) identified a missense mutation in the triple helical domain of the COL8A2 gene (120252.0001), which encodes the alpha-2 chain of type VIII ... In 2 affected members of a family with posterior polymorphous corneal dystrophy, Biswas et al. (2001) identified a missense mutation in the triple helical domain of the COL8A2 gene (120252.0001), which encodes the alpha-2 chain of type VIII collagen, a short-chain collagen that is a component of endothelial basement membranes. They identified the same mutation in familial and sporadic cases of early-onset Fuchs endothelial corneal dystrophy (FECD; 136800). Biswas et al. (2001) suggested that the underlying pathogenesis of FECD and PPCD2 may be related to disturbance of the role of type VIII collagen in influencing the terminal differentiation of the neural crest-derived corneal endothelial cell. In a family in which 1 member had PPCD2 and other members had early-onset FECD, Gottsch et al. (2005) found that all affected individuals were heterozygous for a leu450-to-trp (L450W) substitution (120252.0003).