CPS1D is a rare metabolic condition with a nonspecific biochemical profile thus requiring additional tests.5 Nowadays, confirmation of the disease is usually done by molecular genetic investigation that led to the reporting of more than 230 CPS1 mutations underlining the genetic heterogeneity at this locus.7, 8, 9, 10, 11, 12, 13, 14 In recent years, NGS became the preferred method for CPS1 molecular genetic investigation either as part of (often custom‐made) gene panels or of whole exome or genome sequencing. This evidence concerns the gene CPS1 and carbamoyl phosphate synthetase I deficiency disease.