The TGFBI R555W mutation induces a new granular corneal dystrophy type I phenotype

PURPOSE To report the clinical and molecular features of a distinct form of transforming growth factor-β-induced (TGFBI) gene-linked corneal dystrophy exhibiting a new granular corneal dystrophy type I (CDGG1) phenotype. METHODS A complete ophthalmologic examination was performed in all individuals of a Chinese family in which autosomal dominant transmission of the disease had been observed. DNA was obtained from the peripheral blood leukocytes of each participating subject. Genetic analyses included keratin 3 (KRT3), keratin 12 (KRT12), and TGFBI polymerase chain reaction (PCR) amplification and automated nucleotide sequencing of exons from the genomic DNA. RESULTS The corneal phenotype in this pedigree was characterized by multiple bilateral dot-like, circular opacities at different corneal depths, with some of the affected individuals only having opacities in the epithelium, which is different from the typical CDGG1 phenotype. TGFBI analysis revealed a heterozygous point mutation at exon 12 (c.1663C>T) in all of the affected individuals, predicting a p.R555W missense mutation. CONCLUSIONS The phenotype which resulted from the TGFBI R555W mutation in this family is distinct from that observed in the typical case of CDGG1. We propose this disorder should be classified as a new phenotype of CDGG1, and this finding demonstrates the importance of gene diagnosis in the corneal dystrophies.