Urea cycle disorders can be caused by a deficiency of carbamoyl phosphate synthetase I (CPS1), ornithine transcarbamylase (OTC), argininosuccinate synthetase (citrullinemia), argininosuccinate lyase (argininosuccinic aciduria), arginase I (argininemia) or N-acetylglutamate synthetase (NAGS). The earlier the enzyme deficiency occurs in the cycle, the more pronounced the hyperammonemia. With an incidence of 1:14,000, ornithine transcarbamylase (OTC) deficiency is the most common cause.
About half of the urea cycle defects can be diagnosed biochemically. Enzymatic tests can also be carried out, but are usually only possible with invasive procedures to obtain the corresponding test material. Therefore in these cases, genetic diagnosis is recommended.
Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften. S3-Leitlinie: Diagnostik und Therapie von Harnstoffzyklusstörungen. 31.05.2018