Application of high-resolution mass spectrometry profiling towards the diagnosis and acute management of maple syrup urine disease.

The current approach for investigating patients with suspected inborn errors of metabolism (IEMs) involves traditional targeted biochemical assays such as amino/organic acid analyses. Although highly effective for confirmatory testing, they are less effective in identifying disorders not included in newborn screening (NBS) panels, and for patients with non-classical clinical presentations. Targeted assays analyze a narrow range of metabolites and are conducted across different analytical platforms, often requiring more than one specimen type. In contrast, comprehensive metabolic profiling using liquid chromatography-high-resolution mass spectrometry (LC-HRMS) provides significantly more information from a single specimen, eliminating the need for multiple and time-consuming analyses across different platforms. We describe the use of LC-HRMS metabolic profiling in two patients with decompensated maple syrup urine disease (MSUD). In the first patient, a previously healthy 3-month-old infant presenting with altered mental status, apnea, and seizures, LC-HRMS analysis of plasma before treatment showed increased levels of branched-chain amino acids and their related 2-keto and hydroxy acids. The diagnosis of MSUD was confirmed by targeted amino acid analysis. Additionally, the treatment course, which included dialysis and nutritional management, was monitored using LC-HRMS. This approach was successfully applied to a second patient, a 1-week-old infant with classical MSUD identified through NBS. In conclusion, comprehensive metabolic profiling by LC-HRMS is a valuable investigative tool for patients with both classic and non-specific neurometabolic clinical phenotypes, providing additional insights into metabolite perturbations during acute management.