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J. S. Weiss, M. J. Mequio, A. J. Aldave, I. M. Raber, R. C. Eagle, C. Wiaux; Identification of pAsp240Asn Mutation in UBIAD1 Indicates Central Discoid Corneal Dystrophy is Schnyder Corneal Dystrophy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5505.
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© ARVO (1962-2015); The Authors (2016-present)
Mutations in the UBIAD1 gene on chromosome 1 were recently discovered to be causative of Schnyder corneal dystrophy (SCD). We sought to determine whether the entity described as Central Discoid Corneal Dystrophy (CDCD) is SCD through screening of UBIAD1 in the family previously reported to have CDCD.
DNA was collected from five members of the family previously reported to have CDCD. The UBIAD1 coding region was screened in all individuals, as well as 250 control chromosomes.
Three of the five family members were previously diagnosed as affected based on slit lamp examination, while two were reported to be unaffected. Screening of UBIAD1 in the proband revealed a heterozygous p.Asp240Asn mutation, which was also identified in the heterozygous state in the other two affected family members. This mutation was also present in the heterozygous state in one of the proband’s two reportedly unaffected siblings; this individual is scheduled for a slit lamp examination to evaluate for corneal changes consistent with those observed in the affected family members. Screening of 250 control chromosomes did not demonstrate the p.Asp240Asn mutation.
The identification of the p.Asp240Asn missense mutation in UBIAD1 in all affected individuals of the family previously reported to have CDCD indicates that this is likely not a unique corneal dystrophy, but instead SCD. The corneal phenotype of this pedigree was similar to SCD without crystals .The identification of this presumed pathogenic mutation in a reportedly unaffected family member may be explained by the fact that the individual is misclassified as unaffected, the mutation is associated with incomplete penetrance, or it is a private, non-pathogenic variant. Repeat examination of this individual as well as analysis of the effect of the p.Asp240Asn mutation on the function of the protein encoded by UBIAD1 are planned to confirm that this is a pathogenic mutation, and that CDCD is SCD.
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