Corneal microstructural changes of precise CHST6 gene mutation: a case series

Macular corneal dystrophy (MCD) is an inherited, autosomal recessive disorder of defective keratan sulfate (KS) metabolism. It is caused by the mutations in carbohydrate sulfotransferase 6 gene (CHST6) which is essential for the sulfation of KS. Unlike the western world, MCD is the most common corneal stromal dystrophy in India, especially in south Indian population; it could be due to high frequency of consanguineous marriages. This study presents the clinical findings of one North Indian MCD family, including 6 patients and 3 unaffected relatives. We used slit lamp examination and in vivo confocal microscopy for assessment. Mutation screening was performed with Sanger sequencing, and corneal structure was analyzed through histochemistry and immunohistochemistry. Our comparative findings revealed that all the patients identified with the deletion of major portion of CHST6 that included the Open Reading Frame (ORF). Although all the patients showed significantly reduced central corneal thickness (CCT-250 μm), a drastic decrease in stromal keratocyte count, and depletion of Bowman’s layer compared to controls. This study first time revealed that MCD patients from one family with a deletion of major portion of CHST6 that included ORF leads to severe corneal morphological changes.