ZEB1 and posterior polymorphous corneal dystrophy: PPCD has been linked to three chromosomal loci: PPCD1 (OMIM 122000) on chromosome 20p11.2-q11.2, PPCD2 (OMIM 609140) on chromosome 1p34.3 – p32.3, and PPCD3 (OMIM 609141) on chromosome 10p11.2.