Genotypic and phenotypic spectrum of maple syrup urine disease in Zhejiang of China

Background Maple syrup urine disease (MSUD) is an autosomal recessive metabolic disorder originating from defects in the branched-chain alpha-ketoacid dehydrogenase (BCKDH) complex encoded by BCKDHA, BCKDHB and DBT. This condition presents a spectrum of symptoms and potentially fatal outcomes. Although numerous mutations in the BCKDH complex genes associated with MSUD have been identified, the relationship between specific genotypes remains to be fully elucidated. Aim Our objective was to predict the pathogenicity of these genetic mutations and establish potential links between genotypic alterations and the clinical phenotypes of MSUD. Design Retrospective population-based cohort. Methods We analyzed 20 MSUD patients from the Children's Hospital at Zhejiang University School of Medicine (Hangzhou, China), recorded from January 2010 to December 2023. Patients' blood samples were collected by heel-stick through neonatal screening, and amino acid profiles were measured by tandem mass spectrometry. In silico methods were employed to assess the pathogenicity, stability and biophysical properties. Various computation tools were utilized for assessment, namely PredictSNP, MAGPIE, iStable, Align GVGD, ConSurf and SNP effect. Results We detected 25 distinct mutations, including 12 novel mutations. The BCKDHB gene was the most commonly affected (53.3%) compared to the BCKDHA gene (20.0%) and DBT gene (26.7%). In silico webservers predicted all novel mutations were disease-causing. Conclusions This study highlights the genetic complexity of MSUD and underscores the importance of early detection and intervention. Integrating neonatal screening with advanced sequencing methodologies is pivotal in ensuring precise diagnosis and effective management of MSUD, thereby significantly improving the prognosis for individuals afflicted with this condition. [GRAPHICS] .