Thelansis

 Homocystinuria (HCU), arising from a deficiency in cystathionine β-synthase, is an uncommon hereditary condition impacting methionine metabolism. This disorder results in the accumulation of homocysteine due to impaired cystathionine synthesis, leading to various abnormalities across skeletal, cardiovascular, ophthalmic, and central nervous systems. The primary issue lies in the significant reduction of cystathionine β-synthase (CBS) activity, which results in elevated methionine and total homocysteine levels and decreased cystathionine and cysteine. Other disruptions in the methionine metabolic pathway leading to homocystinuria involve remethylation defects, hindering the conversion of homocysteine to methionine. These defects manifest as reduced methionine levels, elevated homocysteine, and sometimes increased methylmalonic acid, except for methylenetetrahydrofolate reductase deficiency, collectively termed cobalamin defects due to their association with vitamin B12 metabolism i...

 Homocystinuria (HCU), caused by cystathionine β-synthase deficiency, is a rare inherited disorder involving the metabolism of methionine. Impaired synthesis of cystathionine leads to accumulation of homocysteine that affects several organ systems leading to abnormalities in the skeletal, cardiovascular, ophthalmic, and central nervous systems. The basic defect is a marked reduction in the activity of the key enzyme for transsulfuration, cystathionine β-synthase (CBS), and is biochemically characterized by elevated methionine and total homocysteine as well as reductions in cystathionine, the immediate product of CBS, and cysteine. Other defects in the methionine metabolic cycle that result in homocystinuria are remethylation defects in which the conversion of homocysteine back to methionine is impaired. These defects produce reduced rather than increased methionine as well as increased homocysteine and may also be associated with an increase in methylmalonic acid. With one exceptio...