OBJECTIVE: To analyze the metabolic profile and genetic variants for newborns with primary carnitine deficiency (PCD) from Guangxi, China. METHODS: From January 2014 to December 2019, 400 575 newborns from the jurisdiction of Guangxi Zhuang Autonomous Region Newborn Screening Center were subjected to tandem mass spectrometry (MS/MS) analysis. Newborns with positive results for PCD and their mothers were recalled for retesting. Those who were still positive were subjected to sequencing of the SLC22A5 gene. RESULTS: Twenty-two newborns and 9 mothers were diagnosed with PCD, which gave a prevalence rate of 1/18 208. Sequencing of 18 newborns and 4 mothers have identified 14 types of SLC22A5 gene variants, with the common ones including c.51C>G (10/44, 22.7%), c.1195C>T (9/44, 20.5%) and c.1400C>G (7/44, 15.9%), The c.517delC(p.L173Cfs*3) and c.1031C>T(p.T344I) were unreported previously and predicted to be pathogenic (PVS1+PM2_supporting+PM3+PP4) and likely pathogenic (PM1+PM2_supporting+PM3+PP3+PP4) based on the American College of Medical Genetics and Genomics standards and guidelines. CONCLUSION c.51C>G, c.1195C>T and c.1400C>G are the most common variants underlying PCD in Guangxi.
Cardiomyopathies ; Carnitine/deficiency* ; China ; Humans ; Hyperammonemia ; Infant, Newborn ; Metabolome ; Muscular Diseases ; Mutation ; Solute Carrier Family 22 Member 5/genetics* ; Tandem Mass Spectrometry

Objective:To explore the characteristics and influencing factors of blood carnitine metabolism in premature infants.Methods:A retrospective analysis of 37 037 neonates with negative results of genetic metabolic disease screening at Guangxi Newborn Disease Screening Center from 2018 to 2021, of which 34 517 normal full-term infants were the control group and 2 520 preterm infants were the research group.According to gestational age, the preterm infants were further divided into three groups: extremely preterm group( n=232), moderately preterm group( n=324)and late preterm group( n=1 964). According to birth weight, they were divided into three groups: very low birth weight group( n=188), low birth weight group( n=1 276)and normal birth weight group( n=1 056). According to blood collection time, they were divided into three groups: 3~7 days group( n=1 990), 8~14 days group( n=342) and 15~28 days group( n=188). Tandem mass spectrometry was used to detect the levels of 31 carnitines in dried blood spots and analyze the differences in the levels of metabolic indicators in each group. Results:Carnitine levels in preterm infants are most affected by gestational age.Adjusting the physiological and pathological conditions of premature infants and other related factors, grouped by gestational age, there were differences in the levels of 31 carnitines among the groups(all P<0.05), the smaller the gestational age, the greater the difference in carnitine levels; grouped by blood collection time, there were statistically significant differences in carnitine levels between preterm infants with different blood collection age groups and full-term 3~7 days groups(all P<0.05), and showing age-related; there are differences among 31 carnitines grouped by body weight(all P<0.05), the smaller the body weight, the greater the difference in carnitine levels.Combined with the analysis of gestational age, birth weight and blood collection date, 17 indicators including C0, C2, C3, C4, C6DC, C10, C10∶1, C12, C12∶1, C14, C14∶1, C14OH, C16, C16∶1, C18, C18∶1 and C18∶1OH are important biomarkers of carnitine metabolism in premature infants. Conclusion:Carnitine in premature newborns has different metabolic differences at different gestational ages, birth weights and blood collection ages, which provides a strong basis for establishing reference standards and interpretation of preterm infants in the laboratory in this region, and provides reasonable and effective early diagnosis and treatment for clinical practice.Meanwhile, it provides an optimized program for timely detection of carnitine deficiency and carnitine supplementation to improve nutrition of premature infants.