Aim - To confirm the mutation of the keratoepithelin gene in patients with a severe form of superficial juvenile granular corneal dystrophy (GCD). Methods - Five Japanese probands in whom GCD was diagnosed after histopathological examination and who developed severe manifestations of GCD in their first decade of life were investigated. Other affected family members of two probands were also examined. All probands were the offspring of consanguineous parents. DNA was extracted from their peripheral blood leucocytes and mutational analysis of the gene was performed by the polymerase chain reaction and direct sequencing. Results - Four of the five probands underwent their first keratectomy or keratoplasty in their teens and subsequently underwent a second or third keratoplasty. Each proband had a homozygous G→A transition at codon 124, replacing Arg→His, of the keratoepithelin gene. Their moderately affected family members were heterozygous for the mutation. Conclusions - This finding suggests that the severity of the corneal phenotype depends on the dose effect of the mutant gene.
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