Urocanic aciduria

A rare metabolic disorder

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

Pathophysiology

Chemical structure of urocanic acid

Urocanic aciduria results from a defect in the histidine catabolic pathway. Normally, histidine is converted to urocanic acid by the enzyme histidine ammonia-lyase. Urocanic acid is then further metabolized by the enzyme urocanase to form 4-imidazolone-5-propionic acid. In individuals with urocanic aciduria, the activity of urocanase is deficient or absent, leading to the accumulation and subsequent excretion of urocanic acid in the urine.

Clinical Presentation

Patients with urocanic aciduria may present with a variety of symptoms, although many individuals remain asymptomatic. When symptoms do occur, they can include developmental delay, intellectual disability, and seizures. The condition is often detected through newborn screening or during the investigation of unexplained developmental issues.

Diagnosis

The diagnosis of urocanic aciduria is typically made through the analysis of urine organic acids using gas chromatography-mass spectrometry (GC-MS). Elevated levels of urocanic acid in the urine are indicative of the disorder. Genetic testing can also be performed to identify mutations in the UROC1 gene, which encodes the urocanase enzyme.

Treatment

Currently, there is no specific treatment for urocanic aciduria. Management of the condition is primarily supportive and focuses on addressing any developmental or neurological symptoms that may arise. Regular monitoring and follow-up with a metabolic specialist are recommended.

Prognosis

The prognosis for individuals with urocanic aciduria varies depending on the severity of symptoms. Many individuals with the condition lead normal lives, especially if they are asymptomatic. However, those with significant developmental or neurological issues may require ongoing support and intervention.

Related pages

• Metabolic disorder
• Histidine
• Urocanase
• Newborn screening