Macular Dystrophy, Corneal (MCD)

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Disease Ontology 12 DOID:2565 OMIM® 57 217800 KEGG 36 H00954 ICD9CM 34 371.55 MeSH 44 D003317 NCIt 50 C34793 SNOMED-CT 67 60258001

ICD10 32 H18.55 ICD10 via Orphanet 33 H18.5 UMLS via Orphanet 71 C0024439 C1636149 Orphanet 58 ORPHA98969 MedGen 41 C1636149 C1691013 SNOMED-CT via HPO 68 2055003 246622003 258211005 373433005 397541004 409668002 41652007 423459005 449734001 5587004 91514001 more UMLS 70 C0024439 C1636149 C1691013

GARD : ²⁰ The following summary is from Orphanet, a European reference portal for information on rare diseases and orphan drugs. Orpha Number: 98969 Definition Macular corneal dystrophy (MCD) is a rare, severe form of stromal corneal dystrophy (see this term) characterized by bilateral ill-defined cloudy regions within a hazy stroma, and eventually severe visual impairment. Epidemiology Prevalence of this form of corneal dystrophy is not known. Cases of MCD have been identified worldwide. The condition is most prevalent in India, Saudi Arabia, Iceland and parts of the USA. Clinical description Whitish opacities in the cornea usually appear during adolescence but may develop in early infancy, or as late as the 6th decade of life. The non-transparent areas progressively merge as the entire corneal stroma becomes cloudy, causing severe visual impairment usually before the 5th decade. The bilateral corneal opacities progressively extend through the entire thickness of the central and peripheral corneal stroma. The corneal stroma is thinner than normal. Etiology Most cases of MCD are caused by mutations in the CHST6 gene (16q22) encoding a protein involved in the production of keratan sulfate, which plays a role in the maintenance of corneal transparency. More than 125 mutations in this gene have been identified to date. Diagnostic methods MCD is characterized histopathologically by intracytoplasmic accumulations of non-sulfated keratan sulfate within the keratocytes and corneal endothelium, sparing the corneal epithelium. MCD is classified as a corneal stromal dystrophy but also involves the Descemet membrane and the corneal endothelium. Differential diagnosis The clinical features of MCD are similar to the corneal involvement found in the systemic mucopolysaccharidoses, such as mucopolysaccharidosis type IH and IS and the mucolipidoses (see these terms). Genetic counseling An autosomal recessive mode of inheritance has been shown in most cases, but some cases are of unknown etiology. Management and treatment Since the condition affects the entire corneal stroma, Descemet membrane and corneal endothelium, lamellar keratoplasty does not excise all damaged tissue. Corneal transplantation may therefore be needed. Vision can be restored by corneal grafting but opacities may recur in the graft after many years.

MalaCards based summary : Macular Dystrophy, Corneal, also known as macular corneal dystrophy, is related to corneal dystrophy, meesmann, 1 and astigmatism. An important gene associated with Macular Dystrophy, Corneal is CHST6 (Carbohydrate Sulfotransferase 6), and among its related pathways/superpathways are Glycosaminoglycan biosynthesis - keratan sulfate and Metabolism. The drugs Fomepizole and Protective Agents have been mentioned in the context of this disorder. Affiliated tissues include eye, endothelial and skin, and related phenotypes are corneal crystals and punctate opacification of the cornea

Disease Ontology : ¹² A corneal dystrophy that is characterized by corneal haze, bilateral loss of vision, eventually necessitating corneal transplantation resulting from progressive punctate opacities in the cornea.

OMIM® : ⁵⁷ Macular corneal dystrophy (MCD) is an autosomal recessive disorder in which progressive punctate opacities in the cornea result in bilateral loss of vision, eventually necessitating corneal transplantation. MCD is classified into 2 subtypes, type I and type II, defined by the respective absence and presence of sulfated keratan sulfate in the patient serum, although both types have clinically indistinguishable phenotypes (summary by Akama et al., 2000). (217800) (Updated 05-Apr-2021)

KEGG : ³⁶ 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.

UniProtKB/Swiss-Prot : ⁷² Macular dystrophy, corneal: An ocular disease characterized by bilateral, progressive corneal opacification, and reduced corneal sensitivity. Onset occurs in the first decade, usually between ages 5 and 9. Painful attacks with photophobia, foreign body sensations, and recurrent erosions occur in most patients. The disease is due to deposition of an unsulfated keratan sulfate both within the intracellular space (within the keratocytes and endothelial cells) and in the extracellular corneal stroma. Macular corneal dystrophy is divided into the clinically indistinguishable types I, IA, and II based on analysis of the normally sulfated, or antigenic, keratan sulfate levels in serum and immunohistochemical evaluation of the cornea. Patients with types I and IA macular corneal dystrophy have undetectable serum levels of antigenic keratan sulfate, whereas those with type II macular corneal dystrophy have normal or low levels, depending on the population examined.

Wikipedia : ⁷³ Macular corneal dystrophy, also known as Fehr corneal dystrophy named for German ophthalmologist Oskar... more...

Clinical features from OMIM®:

217800 (Updated 05-Apr-2021)

Search NIH Clinical Center for Macular Dystrophy, Corneal

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