Urocanic aciduria

Urocanic aciduria
Other names	Urocanate hydratase deficiencyorUrocanase deficiency
Urocanic acid

Urocanic aciduriais anautosomal recessivemetabolic disordercaused by a deficiency of theenzymeurocanase.It is a secondary disorder ofhistidinemetabolism.

Symptoms and signs

Urocanic aciduria is thought to be relatively benign.Although aggressive behavior andmental retardationhave been reported with the disorder,no definitive neurometabolic connection has yet been established.

Genetics

Urocanic aciduria has an autosomal recessive pattern ofinheritance.

Urocanic aciduria has an autosomalrecessiveinheritance pattern, which means the defective gene is located on anautosome,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.

Pathophysiology

Theamino acidhistidine, when catalyzed by the enzymehistidase,formsurocanic acid.Disruptions in this pathway, caused by a deficiency of histidase, is the underlying cause ofhistidinemia.This results in reduced levels of skin andserumurocanic acid, the primary indicator of insufficient histidase activity.

In urocanic aciduria, increased urocanic acid in theurineindicates a deficiency of the enzyme urocanase.

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.

See also

• Inborn errors of metabolism
• Imidazole
• Aromatic amino acids
• Recessive disorders