CLINICAL AND HISTOPATHOLOGIC FEATURES OF CORNEAL DYSTROPHIES IN JAPAN

Purpose: To examine retrospectively the frequency of various corneal dystrophies among Japanese patients who underwent keratoplasty or keratectomy at the authors' institution over a 34-year period, and to compare the histopathologic features of these disorders in the Japanese population with those reported in the Western literature. Methods: Corneal specimens obtained during keratectomy or keratoplasty (lamellar and penetrating) performed at the authors' institution from 1959 through 1992 were reviewed. Immunohistochemical studies were performed using monoclonal antibodies to keratan sulfate and gelsolin, as well as two lectins (concanavalin A and wheat germ agglutinin). Results: Of 1259 corneal specimens, 159 (12.6%) specimens from a total of 80 patients showed corneal dystrophy. Virtually all were non-fuchs dystrophies; only one case of primary Fuchs dystrophy was identified histologically. Granular dystrophy and gelatinous drop-like dystrophy were the most common dystrophies identified in the specimens, largely because of multiple specimens from individual patients with recurrent disease. These two disorders accounted for 86 of the 159 specimens. In terms of numbers of patients, lattice dystrophy was the most common (26 patients, 32.5%), followed by macular dystrophy (16 patients, 20%), gelatinous drop-like dystrophy (15 patients, 18.8%), granular dystrophy (14 patients, 17.5%), and Avellino dystrophy (3 patients, 3.75%). Dystrophies represented by only one or two patients included congenital hereditary endothelial dystrophy, primary spheroidal keratopathy, posterior polymorphous dystrophy, Schnyder crystalline dystrophy, and Fuchs dystrophy. Conclusions: This histopathologic study showed a very low incidence of Fuchs dystrophy in the authors' Japanese patient population, compared with the incidences seen in studies of populations in Western countries. Of the non-fuchs dystrophies, lattice dystrophy was the most common among the patients, although there were large numbers of specimens with granular dystrophy and gelatinous drop-like dystrophy due to their recurrent character. The causes of clinical and histopathologic differences and similarities among the Japanese patients and the patients described in the Western literature are likely related to genetic factors, but a complete understanding of their specific mechanisms awaits future molecular biologic and genetic elucidation.