Identification of six novel mutations in five infants with suspected maple syrup urine disease based on blood and urine metabolism screening

Abstract

Maple syrup urine disease (MSUD) is a rare autosomal recessive genetic metabolic disease, with a high incidence rate in infants. We analyzed the data of molecular genetic analysis of five infants whose metabolism screening suspected MSUD and described their clinical symptoms. Further, we performed next-generation sequencing and Sanger sequencing to determine the genetic causes of the disease. Bioinformatics tools were used to predict the pathogenicity of novel mutations by performing structural modeling. All the five infants showed symptoms before one year of age and had elevated plasma leucine and valine levels. Among them, four infants presented an obvious increase in the urine lactic acid level. We identified the genetic cause of the disease in four infants and analyzed the pathogenicity of six novel mutations, viz., two mutations in BCKDHA (p.Gly180Asp and p.Arg265Gln), three in BCKDHB (p.Tyr169Cys, p.Ala331Thr, and p.Gly336Ser), and one in DBT (p.Leu69Arg), using in silico analysis. We also reviewed previously reported mutations in Chinese patients and summarized their genotypic and phenotypic characteristics. Our study has confirmed or corrected the clinical diagnosis and enriched the mutation spectrum of BCKDHA, BCKDHB, and DBT. We suggest blood and urine metabolism screening combined with next generation sequencing to diagnose MSUD, especially in infants, to achieve early diagnosis and early treatment.

Keywords: Blood and urine metabolism screening; In silico analysis; Maple syrup urine disease; Novel mutation; Secondary structure.