Newly Reported p.Asp240Asn Mutation in UBIAD1 Suggests Central Discoid Corneal Dystrophy Is a Variant of Schnyder Corneal Dystrophy

Purpose: To determine whether central discoid corneal dystrophy (CDCD), previously reported as a novel corneal dystrophy, is actually Schnyder corneal dystrophy (SCD) through screening of the UBIAD1 gene in the members of the family in which CDCD was reported. Methods: Genetic analysis was performed in 3 affected members and 1 unaffected member of a pedigree with CDCD including the affected 31-year-old proband. Results: All 4 affected members of the described pedigree demonstrated discoid central corneal clouding, with subtle, superficial, crystalline deposits noted in one of the affected individuals. Screening of UBIAD1 in the affected individuals demonstrated a previously unreported missense mutation, p.Asp240Asn, which was not identified in an unaffected family member or in 100 control individuals. Conclusions: The clinical findings of the family reported to have CDCD were indistinguishable from those found in SCD. However, CDCD was originally thought to be distinct from SCD because of the absence of positive lipid staining and the presence of alcian blue staining consistent with glycosaminoglycans in the proband's cornea. Our recent investigation has revealed that corneal specimens from other patients with SCD have also demonstrated staining for glycosaminoglycans. Discovery that mutations in UBIAD1 caused SCD allowed genetic testing of this CDCD family. Our newly reported UBIAD1 mutation suggests that CDCD is actually a variant of SCD. This report underscores the utility of genetic testing in determining whether newly described corneal dystrophies are in fact unique entities or just variants of well-known diseases.