The urocanase deficiency is caused by mutations in the UROC1 gene, which are transmitted in an autosomal recessive manner. To date, four mutations have been described in two different families: c.209T>C (p.L70P) and c.1348C>T (p.R450C); and c.356C>G (p.P11R) and c.907G>C (p.A303P).
Urocanase deficiency is an inborn error of histidine metabolism. The urocanase catalyzes the conversion of urocanic acid to imidazolnepropionic acid. Therefore, a defective urocanase would cause the accumulation of acid urocanic, leading to urocanic aciduria.
The diagnostic testing consists of the analysis of the 21 codified exons of the UROC1 gene. This study can be performed by Sanger sequencing if only this gene is going to be analysed. However, if the clinical diagnosis is not clear, and other genes that could cause a similar phenotype are going to be analysed, a NGS (Next Generation Sequencing) approach must be considered, such as a targeted capture for sequencing specific genomic regions.