Abstract
Abstract: :
Purpose: Macular corneal dystrophy (MCD ; OMIM 217800) is an autosomal recessive disorder which is rare in Europe. The onset occurs in the first decade of life and MCD patients developp progressive punctate bilateral opacities in the corneal stroma associated with a general diffuse haze, leading to visual impairement. MCD is classified into two phenotypically identical subtypes based on whether sulphated keratan sulfate (KS) is present or absent in corneal tissue or blood serum. Recently mutations in the carbohydrate sulfotransferase 6 gene (CHST6), encoding an enzyme designated N-acetylglucosamine-6-sulfotransferase, were identified in MCD patients. In MCD type I mutations in the coding region of the CHST6 gene were found, whereas large deletions and/or replacements in the upstream region of CHST6 resulted in MCD type II. Methods: Patients from twelve unrelated French families were screened for mutations in the CHST6 gene by using automated sequencing of PCR-amplified genomic DNAs as described by Okama et al. Results: No genomic rearrangements in the 5'-non coding region of the CHST6 gene was detected, whilst all mutations appeared to be private variants located within the coding region of CHST6. Among the patients, we identified 12 different point mutations, one of which was previously reported in Icelandic patients, and the others were all new including small deletions and insertions, missense mutations as well as two distinct nonsense mutations. Conclusion: However besides these stereotyped forms, differential histologic diagnosis of atypical forms remains difficult and these forms could be misdiagnosed. The characteristic biomicroscopic appearance of each dystrophy could not provide an accurate diagnosis. Atypical forms are unequivocally diagnosed after DNA analysis.
Keywords: 370 cornea: basic science • 420 genetics • 374 cornea: stroma and keratocytes