Macular corneal dystrophy type 1 and 2 (Macular dystrophy corneal type 1 and 2) - Gen CHST6.

Macular corneal dystrophy an eye disease characterized by progressive bilateral corneal opacification, and reduced corneal sensitivity. Onset occurs in the first decade, usually between 5 and 9 years old. In most painful episodes affected with photophobia, foreign body sensation and recurrent erosions occur. The disease is due to the deposition of a keratan sulfate-sulfated not both within the intracellular space (within keratinocytes and endothelial cells) and the stroma cornealextracelular. This alteration is divided into types I, IA and II according to the analysis of sulfated normal, or antigenic keratan sulfate concentrations in serum and immunohistochemical evaluation of the cornea. Individuals with Type I and IA corneal macular dystrophy have detectable serum antigenic keratan sulfate, while type II have normal or low concentrations.

Corneal macular dystrophy is due to mutations in the gene CHST6, located on the long arm of chromosome 16 (16q22). The protein encoded by this gene is an enzyme that catalyzes the transfer of a sulfate group to keratan GlcNAc residues. Keratan sulfate plays a central role in the maintenance of corneal transparency.

They have been identified homozygous missense mutations in the CHST6 gene in people with macular corneal dystrophy type I, while mutations in the CHST6 gene in people with type II show a large deletion and substitution in the upstream region of the gene CHST6 . The single missense mutation for type II is Cys-50, which is heterozygous with a substitution in the proximal region on the other allele CHST6. Mutations in the gene cause inactivation of the enzyme or results in the loss of function of the corneal sulfa transferase.

This disease is inherited in an autosomal recessive pattern, that is, both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.

Tests in IVAMI: in IVAMI perform detection of mutations associated with macular corneal dystrophy, by complete PCR amplification of the exons of the gene CHST6, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).