Macular corneal dystrophy, also known as Fehr corneal dystrophy named for German ophthalmologist Oskar Fehr (1871-1959), is a rare pathological condition affecting the stroma of cornea. The first signs are usually noticed in the first decade of life, and progress afterwards, with opacities developing in the cornea and attacks of pain. The condition was first described by Arthur Groenouw in 1890. Signs and symptoms
Onset occurs in the first decade, usually between ages 5 and 9. The disorder is progressive, vision changes with ageing from 2nd decade to 3rd visual impairment may seen in 4th and 5th decade severe visual impairment can be seen Minute, gray, punctate opacities develop. Corneal sensitivity is usually reduced. Painful attacks with photophobia, foreign body sensations, and recurrent erosions occur in most patients. Macular corneal dystrophy is very common in Iceland and accounts for almost one-third of all corneal grafts performed there. Genetics
Macular corneal dystrophy is inherited in autosomal recessive fashion and is thought to be caused by the lack or abnormal configuration of keratan sulfate. Most cases of MCD are caused by mutations in CHST6 gene.The gene CHST6 is a carbohydrate sulfotransferase encoding an enzyme designated corneal N-acetylglucosamine-6-sulfotransferase. In MCD type I, various mutations lead to inactivation of the enzyme, in MCD type II, inactivation is caused by large deletions and/or replacements in the gene. Diagnosis
Treatment
Corneal transplantation is often required. See also
Corneal dystrophy

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Metastatic disease is considered life-threatening to the patient.According to the NCI Drug Dictionary, "tazemetostat is an orally available, small molecule selective and S-adenosyl methionine (SAM) competitive inhibitor of histone methyl transferase EZH2, with potential antineoplastic activity. Upon oral administration, tazemetostat selectively inhibits the activity of both wild-type and mutated forms of EZH2. Inhibition of EZH2 specifically prevents the methylation of histone H3 lysine 27 (H3K27). This decrease in histone methylation alters gene expression patterns associated with cancer pathways and results in decreased tumor cell proliferation in EZH2 mutated cancer cells. EZH2, which belongs to the class of histone methyltransferases (HMTs), is overexpressed or mutated in a variety of cancer cells and plays a key role in tumor cell proliferation. "The U.S. Food and Drug Administration (FDA) considers it to be a first-in-class medication. History
The U.S. Food and Drug Administration (FDA) approved tazemetostat in January 2020, based on the results of a clinical trial (NCT02601950) enrolling 62 subjects with metastatic or locally advanced epithelioid sarcoma. During the clinical trial, subjects received 800 milligrams (mg) of tazemetostat twice a day until the disease progressed or the subject reached an unacceptable level of toxicity. Tumor response assessments were performed every eight weeks during the clinical trial. The trial measured how many subjects experienced complete or partial shrinkage (by a certain amount) of their tumors during treatment (overall response rate). The overall response rate was 15%, with 1.6% of subjects having a complete response and 13% having a partial response.