CHST6 and macular corneal dystrophy: Other MCD causing mutations are nucleotide insertions or deletions in the coding region of CHST6 that cause frameshift changes as well as a few deletions or substitutions upstream between CHST5 and CHST6. The molecular basis for the different immunophenotypes remains to be determined and a molecular genetic study of MCD in Saudi Arabia found identical CHST6 mutations in families with MCD type I, IA and II [60].