Urocanic aciduria

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Urocanic aciduria Classification and external resources
Urocanic acid
ICD-10	E70.8
ICD-9	270.5
OMIM	276880
DiseasesDB	32605
MeSH	D014560

Urocanic aciduria, also called urocanate hydratase deficiency or urocanase deficiency,^[1] is an autosomal recessive metabolic disorder caused by a deficiency of the enzyme urocanase. It is a secondary disorder of histidine metabolism.^[2]

Contents 1 Pathophysiology 2 Symptoms 3 Genetics 4 See also 5 References

[edit] Pathophysiology

The amino acid histidine, when catalyzed by the enzyme histidase, forms urocanic acid. Disruptions in this pathway, caused by a deficiency of histidase, is the underlying cause of histidinemia. This results in reduced levels of skin and serum urocanic acid, the primary indicator of insufficient histidase activity.

In urocanic aciduria, increased urocanic acid in the urine indicates a deficiency of the enzyme urocanase. This enzyme breaks down urocanic acid, forming formininoglutamic acid, and also forms imidazolonepropionic acid from trans-urocanic acid.

With normal to only slightly elevated levels of histidine present in the liver during urocanic aciduria, the only true metabolic indicator of the disorder can be found in the urine.^[2]

[edit] Symptoms

Urocanic aciduria is thought to be relatively benign.^[2] Although aggressive behavior and mental retardation have been reported with the disorder,^[3] no definitive neurometabolic connection has yet been established.^[2]

[edit] Genetics

Urocanic aciduria has an autosomal recessive inheritance pattern, which means the defective gene is located on an autosome, and two copies of the gene - one copy inherited from each parent - are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but are usually not affected by the disorder.

[edit] See also

• Inborn errors of metabolism
• Imidazole
• Aromatic amino acids

[edit] References

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 - Alkaptonuria - Ochronosis - Tyrosinemia (Hawkinsinuria) Tetrahydrobiopterin deficiency 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