A rare, inherited condition caused by an enzyme deficiency. Homocystinuria is a type of inborn error of metabolism (see metabolism, inborn errors of) in which there is an abnormal presence of homocystine (an amino acid) in the blood and urine. Affected people are very tall, with long limbs and fingers. Some have skeletal deformities and abnormalities of the eye lens. The condition is incurable but may be improved by a special diet.
Homocystinuria is a congenital disease due to the inability of the affected individual to metabolise, or to utilise properly, one of the essential AMINO ACIDS known as methionine. The main features of the condition are abnormality of the lens of the EYE, learning disability, and a tendency to thromboses (blood clots).
n. an *inborn error of metabolism, inherited as an autosomal *recessive trait, caused by an enzyme deficiency resulting in an excess of *homocysteine in the blood and the presence of homocystine in the urine. Clinically affected individuals have learning disabilities, are excessively tall with long fingers (due to overgrowth of bones), generally have loose ligaments (which may result in dislocation of the lens), and have a tendency to form blood clots in the veins and arteries, leading to strokes. Treatment is by diet, which may allow for normal development if the disease is recognized early enough, and high-dose vitamin B6 therapy.
n. a sulphur-containing amino acid that is an intermediate in the synthesis of *cysteine. A deficiency in the enzyme cystathionine synthetase results in elevated levels in the blood of homocysteine and homocystine (an oxidized form of homocysteine), resulting in elevated urinary levels (see homocystinuria). It is becoming increasingly recognized that elevated levels of homocysteine in the blood are a risk factor for vascular disease independent of diabetes, hypertension, elevated levels of cholesterol in the blood, and smoking. Levels are also elevated in vitamin B12 deficiency.... homocysteine
any one of a group of inherited conditions in which there is a disturbance in either the structure, synthesis, function, or transport of protein molecules. There are over 1500 inborn errors of metabolism; examples are *phenylketonuria, *homocystinuria, and *hypogammaglobulinaemia.... inborn error of metabolism
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