Acute encephalopathy in a neonate: a diagnostic odyssey leading to maple syrup urine disease (MSUD).

We report a rare case of a term neonate presented with seizure, encephalopathy and respiratory distress, with an initial sepsis screen, serum electrolytes, blood sugar and cerebrospinal fluid (CSF) examination revealing no abnormalities. However, CT scan and MRI showed diffuse brain white matter oedema, and tandem mass spectroscopy and gas chromatography revealed elevated levels of branched chain amino acids and their ketoacids and hydroxy acids in urine. Clinical exome sequencing confirmed a mutation in the BCKDHB gene, diagnosing classical variety of maple syrup urine disease (MSUD). The baby was managed with high glucose infusion and a specialised branched-chain amino acid-free formula. This case highlights the importance of considering inborn error of metabolism (IEM) in neonates with encephalopathy and negative sepsis screens, using advanced imaging and metabolomics for timely and accurate diagnosis, prompt management to prevent ongoing encephalopathy and optimise long-term neurodevelopmental outcome. Early recognition and intervention in IEM cases can significantly impact patient outcomes, highlighting the need for a multidisciplinary approach to diagnosis and treatment.