Abstract：Objective To investigate the clinical features of one pair of twin neonates with maple syrup urine disease (MSUD) in the Chinese Han population and pathogenic mutations in related genes, and to provide guidance for the early diagnosis and treatment of MSUD. Methods The clinical and imaging data of the twin neonates were collected. The peripheral blood samples were collected from the twin neonates and their parents to detect the genes related to MSUD (BCKDHA, BCKDHB, DBT, and DLD). The loci with gene mutations were identified, and a bioinformatic analysis was performed. Results Two mutations were detected in the BCKDHB gene, missense mutation c.304G > A (p.Gly102Arg) and nonsense mutation c.331C > T (p.Arg111*), and both of them were heterozygotes. The mutation c.304G > A (p.Gly102Arg) had not been reported in the world. Their father carried the missense mutation c.304G > A (p.Gly102Arg), and their mother carried the nonsense mutation c.331C > T (p.Arg111*). Conclusions The c.331C > T (p.Arg111*) heterozygous mutation in BCKDHB gene is the pathogenic mutation in these twin neonates and provides a genetic and molecular basis for the clinical features of children with MSUD.
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