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elevated levels of ammonia or its compounds in the blood. A congenital form occurs in two types: Type 1, due to deficiency of the enzyme ornithine carbamoyltransferase, is marked by vomiting, lethargy, coma, and hepatomegaly; symptoms are aggravated by protein ingestion. Type 2, due to deficiency of the enzyme carbamoyl phosphate synthetase (ammonia), is marked by vomiting, lethargy, and flaccidity and by elevated plasma and urinary levels of glycine. Hyperammonemia may also occur in nongenetic diseases such as severe liver disease.
am·mo·ne·mi·a, ammoniemia (am'ō-nē'mē-ă, am'ō-ne-ē'mē-ă),
The presence of ammonia or some of its compounds in the blood, thought to be formed from the decomposition of urea; it usually results in subnormal temperature, weak pulse, gastroenteric symptoms, and coma.
[ammonia + G. haima, blood]
hyperammonemia/hy·per·am·mo·ne·mia/ (-am″o-ne´me-ah) a metabolic disturbance marked by elevated levels of ammonia in the blood.
Etymology: Gk, hyper + (ammonia), haima, blood
abnormally high levels of ammonia in the blood. Ammonia is produced in the intestine, absorbed into the blood, and detoxified in the liver. It is also generated as a by-product of protein metabolism. An increased production of ammonia or a decreased ability to detoxify it increases the blood levels of ammonia. The disorder is controlled by low-protein diets, including essential amino acid mixtures. Untreated, the condition leads to hepatic encephalopathy, characterized by asterixis, vomiting, lethargy, coma, and death.
hyperammonemiaMetabolism A heterogeneous group of five largely AR inborn errors of metabolism; each has a defect in a urea cycle enzyme–arginase, argininosuccinase, argininosuccinic acid synthetase, carbamyl phosphate synthetase, ornithine transcarbamylase; all begin in late infancy or childhood, except arginase deficiency, which is neonatal Clinical Accumulation of urea precursors–eg, ammonia, glutamine causes progressive lethargy, hyperthermia, apnea, hyperammonemia Diagnosis may be established in utero by restriction fragment–RFLP analysis Treatment Restrict dietary protein; activate alternate pathways of waste nitrogen excretion–eg, sodium benzoate or dietary supplementation with arginine
1. the presence of ammonia in excess of the normal range of concentration of ammonia in the blood.
2. a metabolic disorder marked by elevated levels of ammonia or ammonium ion in the blood. One of the effects of severe hepatic dysfunction. May cause hepatic encephalopathy.