Estimating the Prevalence of Granular Corneal Dystrophy Type 2 (Avellino Corneal Dystrophy) in Korea

Abstract

Purpose: : In this study, we used modeling to estimate the prevalence of granular corneal dystrophy type 2 (GCD2; Avellino corneal dystrophy), a rare disease, in the Korean population.

Methods: : Through a collaboration of Korean referral centers for corneal disease, we identified all GCD2 homozygotes that were over the age of three in 2005. The genetic status of the patients and their immediate families were verified by DNA analysis. We developed a model based on the Hardy-Weinberg principle to calculate a lower bound for the gene prevalence. We developed a second, population-based model to correct for known underestimation in the primary model. Both models used population data from the 2005 Korean census and the corrected model also used fertility rates from historical Korean census data.

Results: : We identified 21 individuals homozygous for GCD2 (R124H mutation) from 16 Korean families. From this, we estimate that the overall prevalence (combining heterozygotes and homozygotes) is at least 8.25 affected persons/10,000 persons. Based on our corrected estimate, the overall prevalence is likely to be greater than 11.5 affected persons/10,000 persons.

Conclusions: : We present the first estimate of the prevalence of GCD2. Although uncommon, the prevalence of GCD2 in Korea is greater than anticipated. We believe that our approach could potentially be applied to estimating the prevalence of other rare diseases.

Keywords: cornea: clinical science • degenerations/dystrophies