A mutation within exon 14 of the TGFBI (BIGH3) gene on chromosome 5q31 causes an asymmetric, late onset form of lattice corneal dystrophy

Purpose: Two forms of autosomal-dominant lattice corneal dystrophy (LCD), t ypes I and IIIA, have previously been shown to be caused by different mutat ions within the transforming growth factor, beta-induced (TGFBI) gene. A cl inical and molecular analysis of three unrelated kindreds with a clinically distinct late-onset LCD was undertaken to determine whether this phenotype is also caused by mutations within the TGFBI gene. Design: Experimental study. Participants: Thirty-two members of three kindreds with corneal dystrophy, DNA from 100 normal control subjects was used as a control population. Methods: Members of three kindreds with LCD were examined clinically, and b lood samples were taken for DNA analysis. Mutation analysis was undertaken on all individuals for the coding region of the TGFBI gene by means of poly merase chain reaction (PCR) followed by single-stranded conformation polymo rphism/heteroduplex analysis, subcloning, and sequencing. Main Outcome Measures: Detection of mutations within the TGFBI gene. Results: Clinical examination revealed a form of LCD that was bilateral in all but one case, with onset around the fourth to fifth decade. The majorit y of cases showed significant asymmetry, and in one case there was evidence of onset directly after minor superficial corneal trauma. Molecular analys is in all families demonstrated sequence changes within exon 14 of the TGFB I gene on chromosome 5q31, at codon 622 in family 3, and at codon 626 in fa milies 1 and 2, which are presumed to be responsible for the disease. Conclusions: Previously, a late-onset form of LCD, termed IIIA, was shown t o be caused by a P501T mutation in exon 11 of TGFBI. The authors present th e first description of mutations in exon 14 of TGFBI causing an LCD, also o f late onset. Although the condition presented is morphologically and histo pathologically typical of an isolated lattice dystrophy, the age of onset a nd clinical course is not typical of type I, III, or IIIA lattice dystrophy , This, in conjunction with recent developments in our understanding of the molecular genetics of these disorders, calls into question the usefulness and validity of the current classification of the isolated lattice dystroph ies.