Treatment strategies, radiological recovery, and neurodevelopmental outcomes in paediatric Maple Syrup Urine Disease: a 20-year single-centre experience from Türkiye.

Maple Syrup Urine Disease (MSUD) is a rare autosomal recessive metabolic disorder characterised by defective branched-chain amino acid (BCAA) catabolism, leading to neurotoxicity, recurrent metabolic crises, and neurodevelopmental impairment. Evidence on long-term outcomes in paediatric cohorts, particularly with pharmacological adjuncts such as sodium phenylbutyrate (NaPBA) and radiological recovery, remains limited. We undertook a retrospective review of 13 paediatric patients with MSUD (69.2% classic phenotype, 30.8% intermittent) followed at a tertiary metabolic centre in Türkiye between 2003 and 2022. Demographic, biochemical, neurodevelopmental, neuroimaging, and genetic data were evaluated, with specific attention to dietary management, haemodialysis during acute decompensation, and NaPBA therapy. All patients exhibited neurodevelopmental delay, which was more pronounced in the classic phenotype. Milestone-level analysis demonstrated delays in walking (85%), sentence formation (92.3%), and toilet training (92.3%). One year after dietary intervention, mean plasma concentrations of leucine, isoleucine, and valine decreased by 60.9%, 55.9%, and 65.0%, respectively (p < 0.01). Haemodialysis during metabolic crises rapidly reduced leucine (- 73.8%) and ammonia (- 66%), though was more frequently required in patients with the classic phenotype. NaPBA treatment was associated with lower leucine levels during follow-up (p < 0.05). Baseline MRI abnormalities were identified in 87% of patients; 57% showed complete resolution post-treatment, with partial radiological improvement observed alongside clinical follow-up. A phenotype-specific approach combining early dietary intervention, timely haemodialysis in acute crises, and selective use of NaPBA may support metabolic stabilisation and radiological improvement in selected patients. Larger multicentre studies are warranted to validate these findings and refine management protocols.