Hyperammonemia

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Hyperammonemia Classification and external resources
Ammonia
ICD-10	E72.2
ICD-9	270.6
DiseasesDB	20468
eMedicine	neuro/162  ped/1057
MeSH	D022124

Hyperammonemia (or 'hyperammonaemia') is a metabolic disturbance characterised by an excess of ammonia in the blood. It is a dangerous condition that may lead to encephalopathy and death. It may be primary or secondary.

Ammonia is a substance that contains nitrogen. It is a product of the catabolism of protein. It is converted to the less toxic substance urea prior to excretion in urine by the kidneys. The metabolic pathways that synthesise urea are located first in the mitochondria and then into the cytosol. The process is known as the urea cycle, which comprises several enzymes acting in sequence.

Contents 1 Types 1.1 Primary vs. secondary 1.2 Specific types 2 Sequelae 3 See also 4 External links

[edit] Types

[edit] Primary vs. secondary

• Primary hyperammonemia is caused by several inborn errors of metabolism that are characterised by reduced activity of any of the enzymes in the urea cycle.
• Secondary hyperammonemia is caused by inborn errors of intermediary metabolism characterised by reduced activity in enzymes that are not part of the urea cycle (e.g .Propionic acidemia, Methylmalonic acidemia) or dysfunction of cells that make major contributions to metabolism (eg hepatic failure).

[edit] Specific types

The following list includes such examples:

• Online 'Mendelian Inheritance in Man' (OMIM) 311250 - hyperammonemia due to ornithine transcarbamylase deficiency
• Online 'Mendelian Inheritance in Man' (OMIM) 606762 - hyperinsulinism-hyperammonemia syndrome (glutamate dehydrogenase 1)
• Online 'Mendelian Inheritance in Man' (OMIM) 238970 - hyperornithinemia-hyperammonemia-homocitrullinuria syndrome (ornithine translocase)
• Online 'Mendelian Inheritance in Man' (OMIM) 237310 - hyperammonemia due to N-acetylglutamate synthetase deficiency
• Online 'Mendelian Inheritance in Man' (OMIM) 237300 - hyperammonemia due to carbamoyl phosphate synthetase I deficiency (carbamoyl phosphate synthetase I)
• Online 'Mendelian Inheritance in Man' (OMIM) 238750 - hyperlysinuria with hyperammonemia (genetics unknown)
• Methylmalonic acidemia
• Isovalemic acidemia
• Propionic acidemia

[edit] Sequelae

Hyperammonemia is one of the metabolic derangements that contribute to hepatic encephalopathy.

[edit] See also

• Citrullinemia
• N-acetylglutamate synthetase deficiency
• Ornithine translocase deficiency

[edit] External links

• Organic Acidemia Association
• Article on causes of hyperammonemia in the newborn.

v • d • e Inborn errors of amino acid metabolism (E70-72, 270) K Lysine/straight chain Glutaric acidemia type 1 - type 2 - Hyperlysinemia - Pipecolic acidemia - Saccharopinuria Leucine Maple syrup urine disease - Isovaleric acidemia - 3-Methylcrotonyl-CoA carboxylase deficiency - 3-hydroxy-3-methylglutaryl-CoA lyase deficiency G→pyruvate Glycine Sarcosinemia - D-Glyceric acidemia - Glutathione synthetase deficiency G→alpha-ketoglutarate Glutamate/glutamine SSADHD Proline Hyperprolinemia - Prolidase deficiency Histidine Carnosinemia - Histidinemia - Urocanic aciduria G→succinyl-CoA Methionine Hypermethioninemia - Homocystinuria - Cystathioninuria Valine Maple syrup urine disease - Hypervalinemia - Isobutyryl-CoA dehydrogenase deficiency Isoleucine Maple syrup urine disease - Beta-ketothiolase deficiency - 2-Methylbutyryl-CoA dehydrogenase deficiency General BC/OA Propionic acidemia - Methylmalonic acidemia G→fumarate Phenylalanine/tyrosine Phenylketonuria: Tetrahydrobiopterin deficiency - 6-Pyruvoyltetrahydropterin synthase deficiency Tyrosinemia: Type II tyrosinemia - Type III tyrosinemia/Hawkinsinuria - Alkaptonuria/Ochronosis - Type I tyrosinemia G→oxaloacetate Urea cycle/Hyperammonemia (arginine, aspartate) N-Acetylglutamate synthase deficiency - Carbamoyl phosphate synthetase I deficiency - Ornithine transcarbamylase deficiency/translocase deficiency - Citrullinemia - Argininosuccinic aciduria - Argininemia Transport Cystinuria - Hartnup disease - Oculocerebrorenal syndrome - Lysinuric protein intolerance - Inborn errors of renal tubular transport (Cystinosis, Fanconi syndrome) Tyrosine→Melanin Albinism: Ocular albinism - Oculocutaneous albinism (Hermansky-Pudlak syndrome) - Waardenburg syndrome Glycine→Creatine GAMT deficiency Other Trimethylaminuria - 2-Hydroxyglutaric aciduria - Fumarase deficiency see also Amino acid metabolism enzymes, Urea cycle enzymes, intermediates