Macular corneal dystrophy

Macular corneal dystrophy (MCD), inherited in an autosomal recessive fashion, is the least common but severe form of stromal dystrophy characterized by superficial gray-white corneal opacities that progressively increase to involve the entire corneal stroma from limbus to limbus. Patients experience progressive decreased vision and irritation as the diseases worsens, and will have vision severely affected by the third to fourth decade of life. It has been shown that a specific sulfation step in the production of keratan sulfate, the major glycosaminoglycan of the corneal stroma, is impaired in MCD. This results in the accumulation of glycosaminoglycans that form the abnormal deposits. Mutations in the CHST6 gene, which encodes an enzyme that catalyzes the sulfation of keratan sulfate, are responsible for most cases of MCD.