Cystathionine beta-synthase CBS is a crucial enzyme involved in the metabolism of the amino acids methionine and homocysteine. It catalyzes the conversion of homocysteine to cystathionine, which is then further metabolized to cysteine, a non-essential amino acid. This process is part of the transsulfuration pathway, which is essential for the proper functioning of various biochemical processes in the body.A deficiency of CBS disrupts the normal metabolism of methionine and homocysteine. When CBS is deficient, homocysteine cannot be efficiently converted to cystathionine, leading to an accumulation of homocysteine in the body. This excess homocysteine can then be remethylated back to methionine, causing an increase in methionine levels as well. The buildup of homocysteine and methionine in the blood and tissues can have detrimental effects on various organ systems.Homocystinuria is an inherited metabolic disorder caused by a deficiency of CBS. It is an autosomal recessive condition, meaning that an individual must inherit two copies of the defective gene one from each parent to develop the disease. The primary clinical manifestations of homocystinuria are related to the toxic effects of elevated homocysteine levels on the vascular system, connective tissues, eyes, and central nervous system.Some of the common symptoms and complications associated with homocystinuria include:1. Thromboembolic events: Elevated homocysteine levels can cause blood clot formation, leading to life-threatening complications such as stroke, heart attack, and pulmonary embolism.2. Skeletal abnormalities: Patients with homocystinuria often exhibit skeletal abnormalities such as long limbs, scoliosis, and pectus excavatum sunken chest .3. Ocular problems: Dislocation of the lens in the eye ectopia lentis is a common ocular complication in homocystinuria patients, which can lead to vision problems and even blindness if not treated.4. Cognitive impairment: Individuals with homocystinuria may experience developmental delays, learning disabilities, and psychiatric disorders due to the toxic effects of elevated homocysteine levels on the brain.Early diagnosis and treatment of homocystinuria are crucial to prevent or minimize the severity of these complications. Treatment options include dietary modifications to restrict methionine intake, supplementation with vitamins B6, B9 folate , and B12 to promote the remethylation of homocysteine, and, in some cases, the use of medications such as betaine to help lower homocysteine levels.