homocystinuria

homocystinuria /ho·mo·cys·tin·uria/ (-sis″tin-u´re-ah) excessive homocystine in the urine, having various causes, some genetic; symptoms include developmental delay, failure to thrive, neurological abnormalities, and others depending on the cause. Sometimes the term refers specifically to the disorder due to lack of the enzyme cystathionine β-synthase.

---

ho·mo·cys·ti·nu·ri·a (hm-sst-nr-)

n.

An inherited metabolic disorder caused by a deficiency of an enzyme important in the metabolism of homocystine and characterized by the excretion of homocystine in the urine, mental retardation, dislocation of the crystalline lens of the eye, sparse blond hair, and cardiovascular and skeletal deformities.

---

homocystinuria

[hō′mōsis′tinoo͡r′ē·ə]

Etymology: Gk, homos + (cystine); Gk, ouron, urine

a rare biochemical abnormality characterized by the abnormal presence of homocystine, an amino acid, in the blood and urine, which is caused by any of several enzyme deficiencies in the metabolic pathway of methionine to cystine. The disease is inherited as an autosomal-recessive trait. Its clinical signs are similar to those of Marfan's syndrome, including mental retardation, osteoporosis leading to skeletal abnormalities, dislocated lenses, and thromboembolism. Treatment may include a diet low in methionine and supplementation with large doses of vitamin B₆. Long-term results of treatment are not available. homocystinuric, adj.

---

homocystinuria (hō´mōsis´tin-yoo´rē),

n a genetic disorder of amino acid metabolism in which the amino acid homocystine appears in the blood and urine; may respond to a low-protein diet and the administration of synthetic amino acids.

---

homocystinuria

An autosomal recessive inherited disorder caused by a cystathionine beta synthase deficiency, which leads to an accumulation of the amino acid methionine and homocysteine. The first signs are ocular; a dislocated lens which may cause diplopia or glaucoma, myopia and occasionally retinal detachment. Systemic signs are blond hair, intellectual impairment and some of the features of Marfan's syndrome (e.g. tall, thin build).

---

homocystinuria

Metabolic disease An AR condition due to a defect of cystathionine β—synthase , characterized by ↑ (> 300 µmol/L) homocysteine in serum Clinical Overgrowth of long bones, mental retardation, osteoporosis, ectopia lentis, failure to thrive, sparse blond hair, genu valgum, thromboembolism, fatty liver; most die before age 30 of arterial and venous occlusive disease; lesser ↑ of homocysteine is seen in heterozygotes, in those with ↓ folic acid, vitamin B₁₂, in renal failure and after heart transplants Lab ↑ homocysteine in urine Management Pyridoxine or vitamin B₆