Early laboratory indicators of acute metabolic decompensation during emergency presentations in pediatric maple syrup urine disease

Abstract Acute metabolic decompensation (AMD) is the most life-threatening complication of maple syrup urine disease (MSUD). Recognizing AMD early in the emergency department (ED) is difficult because the most important clinical indicators—neurological manifestations—typically appear late during decompensation, and plasma leucine measurements are frequently delayed. This study aimed to identify laboratory biomarkers that can be obtained quickly and support early AMD detection at ED. This retrospective study included MSUD patients aged 28 days–18 years admitted to a tertiary pediatric ED between 2016 and 2025. Acute neurological deterioration, reduced oral intake, or vomiting with ketosis or plasma leucine levels ≥ 600 µmol/L were defined as AMD. Presenting complaints, duration of hospitalization, treatment modalities, and laboratory investigations were recorded and compared between ED visits with AMD and non-AMD. Among 25 patients, 269 ED visits were analyzed; 79 (29.4%) met AMD criteria. AMD visits were associated with worse clinical outcomes, including higher rates of pediatric intensive care admissions (22% vs. 2.6%) and increased hemodialysis requirements (19% vs. 1.6%). Hyponatremia ( p = 0.005) and hyperuricemia ( p < 0.001) were more prevalent during AMD. Acid–base parameters did not significantly discriminate AMD. Among primary laboratory tests, only serum uric acid was a clinically meaningful predictor (AUC 0.786). A cutoff value of 4.65 mg/dL for uric acid was identified to predict AMD. Conclusion : Serum uric acid is a reliable and clinically practical early predictor of AMD. This readily available marker may enable earlier risk stratification and intervention when leucine results are delayed, potentially improving outcomes in pediatric MSUD. What is Known: • Acute metabolic decompensation (AMD) in pediatric maple syrup urine disease (MSUD) can rapidly lead to encephalopathy, cerebral edema, and permanent neurologic injury. • Early emergency presentations are clinically nonspecific, and plasma leucine—the diagnostic gold standard—is often not available in real time. What is New: • A cutoff value of 4.65 mg/dL for uric acid was identified to predict AMD. • Respiratory symptoms and fever were significantly more frequent in non-AMD visits, suggesting that infectious symptoms alone do not necessarily indicate metabolic instability in MSUD patients.