Genotype of Lattice Corneal Dystrophy (R124C Mutation in TGFBI) in a Patient Presenting With Features of Avellino Corneal Dystrophy

Abstract

To present a patient with a genotype usually associated with lattice corneal dystrophy but with clinical and histopathologic features of advanced Avellino corneal dystrophy. Penetrating keratoplasty was performed with subsequent histopathologic analysis. For genetic testing, a 5-mL blood sample was taken after informed consent. Genetic sequencing was performed by the John and Marcia Carver Laboratory of the University of Iowa. The mutation was identified by direct sequencing through the positions of the coding sequences of the TGFBI gene that have been previously reported to have genetic variations (exons 4 and 11-14). Corneal examination revealed bilateral lattice and multiple confluent subepithelial and anterior stromal granular opacities. Histopathologic examination showed amyloid deposits by Congo red stain and hyaline deposits by Masson trichrome stain, consistent with a diagnosis of Avellino dystrophy. Automated DNA sequencing revealed a heterozygous Arg124Cys (R124C) mutation in the coding sequence of the TGFBI gene on chromosome 5q31. Recurrent granular deposits developed in the corneal graft 14 months after surgery. Our case presented with clinical and histopathologic findings consistent with a diagnosis of Avellino dystrophy and exhibited a genotype with R124C mutation. Avellino dystrophy has not previously been reported to be associated with the R124C mutation, which is usually associated with lattice corneal dystrophy. This also raises the issue as to whether classification of the corneal stromal dystrophies should be based primarily on phenotype/histopathology or on genotyping.