Severe corneal dystrophy phenotype caused by homozygous R124H keratoepithelin mutations

To determine the mutational status of the beta ig-h3 gene in five patients from four Japanese families affected with an unusual, severe form of corneal dystrophy. In these five cases, the corneas were remarkable for confluent round opacities in the superficial stromal layer. The beta ig-h3 gene coding for keratoepithelin was recently identified as the gene responsible for 5q-linked autosomal dominant corneal dystrophies.

Genomic DNA was isolated from leukocytes of five patients with the severe form of corneal dystrophy. To screen for point mutations, exons of the beta ig-h3 gene were amplified by polymerase chain reaction and were analyzed with the single-strand conformational polymorphism technique. Subsequently, the mutations were identified by a direct sequencing method and restriction enzyme digestion analysis.

All five patients with the severe form of corneal dystrophy had homozygous R124H keratoepithelin mutations. Histopathologic examinations of the corneas obtained from two patients with the severe form showed granular, rod-shaped deposits.

The severe phenotype was a pathologic variant of granular corneal dystrophy (GCD). All five patients had homozygous R124H keratoepithelin mutations. The R124H keratoepithelin mutation is the same mutation recently reported to be responsible for Avellino corneal dystrophy. The homozygous R124H keratoepithelin mutations are the cause of the severe variant of GCD characterized by juvenile-onset and confluent superficial opacity.