Molecular genetic study of Egyptian patients with macular corneal dystrophy.

Abstract

To identify the underlying genetic defect in Egyptian patients with macular corneal dystrophy (MCD). A clinical and molecular genetic study was performed on 11 patients from six families with MCD. Clinical diagnosis was confirmed by slit-lamp biomicroscopy and histopathological examination of corneal buttons following keratoplasty. The coding region of the carbohydrate sulfotransferase (CHST6) gene was amplified by polymerase chain reaction (PCR) in all affected subjects. This was followed by direct sequencing and restriction digest analyses. Enzyme-linked immunosorbent assay of antigenic keratan sulfate (KS) in patients' serum was also performed. Six homozygous mutations, of which three are novel, were identified within the coding region of CHST6 in six unrelated MCD families. The barely detectable level of antigenic KS in the serum of the affected individuals indicated that they all have MCD type I, including the subtype IA. This is the first report of a molecular genetic analysis of MCD in the Egyptian population. These data indicate the extensive allelic heterogeneity within CHST6 and further support its essential role in maintaining corneal transparency.