Abstract: Objective To detect blood acylcarnitine and genes in a newborn with suspected citrullinemia, and to detect gene mutations in their parents, so as to clarify their diagnosis and follow-up investigations. Methods Genetic metabolic diseases were screened in the newborn baby using tandem mass spectrometry. Peripheral blood samples were collected from the newborn patient with suspected citrullinemia to detect the products of genetic metabolic diseases. Peripheral blood samples were collected from newborns and their parents for high-throughput sequencing and Sanger sequencing. The blood samples of the newborns and their parents were sequenced and verified, and then the genetic abnormalities were analyzed. Results Tandem mass spectrometry showed that the level of citrulline increased(1 043 μmol/L), the level of citrulline increased to 2 072 μmol/L after recall immediately. Double heterozygous mutations of ASS1 gene in the proband were identified:c.256C＞T and c.577G＞A,which were confirmed in the parents.The case was diagnosed with citrullinemia type Ⅰ. Conclusions Neonatal tandem mass spectrometry, in combination with a pedigree analysis of the gene sequencing, may support the diagnosis of citrullinemia.

Key words: citrullinemia, ASS1 gene, tandem mass spectrometry