Urocanic aciduria

A rare metabolic disorder

Urocanic aciduria is a rare metabolic disorder characterized by the accumulation of urocanic acid in the urine. This condition is caused by a deficiency of the enzyme urocanase, which is involved in the histidine degradation pathway.

Biochemistry

Urocanic acid is an intermediate in the catabolism of the amino acid histidine. Normally, histidine is converted to urocanic acid by the enzyme histidine ammonia-lyase, and then urocanic acid is further metabolized by urocanase to form 4-imidazolone-5-propionic acid. In individuals with urocanic aciduria, the deficiency of urocanase leads to the accumulation of urocanic acid, which is then excreted in the urine.

Genetics

Urocanic aciduria is inherited in an autosomal recessive manner. This means that an affected individual must inherit two copies of the defective gene, one from each parent. The parents of an affected individual are typically carriers, meaning they each carry one copy of the mutated gene but do not show symptoms of the disorder.

Urocanic aciduria is inherited in an autosomal recessive pattern.

Clinical Features

Most individuals with urocanic aciduria are asymptomatic and the condition is often discovered incidentally during metabolic screening. In rare cases, it may be associated with developmental delay or other neurological symptoms, but the clinical significance of these findings is not well established.

Diagnosis

The diagnosis of urocanic aciduria is typically made by detecting elevated levels of urocanic acid in the urine. This can be done using gas chromatography-mass spectrometry (GC-MS) or other biochemical assays. Genetic testing can confirm the diagnosis by identifying mutations in the gene encoding urocanase.

Management

There is no specific treatment for urocanic aciduria. Management is generally supportive and focuses on monitoring for any potential complications. Genetic counseling may be offered to affected families to discuss inheritance patterns and risks for future pregnancies.

Related pages

• Metabolic disorder
• Amino acid metabolism
• Inborn errors of metabolism

References

Structure of urocanic acid.