Acute Encephalopathy in a 10-Year-Old Patient With Maple Syrup Urine Disease: A Challenging Diagnosis

Maple syrup urine disease (MSUD) is a rare autosomal recessive metabolic disorder characterized by a deficiency in the branched-chain alpha-keto acid dehydrogenase complex, leading to the toxic accumulation of leucine, isoleucine and valine. Acute encephalopathy (AE) is a severe neurological disorder with diverse etiologies, demanding prompt identification and intervention. We present a unique case of a previously healthy teenage patient who developed AE during an influenza infection. Despite initial inconclusive investigations, the patient's condition rapidly deteriorated, requiring pediatric intensive care unit (PICU) admission. Diagnostic challenges included fluctuating mental status and refractory intracranial hypertension, ultimately necessitating decompressive craniectomy. Empirical treatments, including corticosteroids, tocilizumab, and plasmapheresis, were administered. Finally, clinical exome analysis revealed a pathogenic variant in homozygosity in the BCKDHA gene associated with MSUD type Ia. Her adult sister, experiencing similar symptoms in the same time period, did not survive. This case underscores the importance of considering metabolic disorders in AE etiology, even accounting for its various associated syndromes and usual prolonged diagnostic investigation, as prompt treatment initiation is vital for improved outcomes. Management of AE involves addressing seizures, systemic support and neuromonitoring, namely, intracranial pressure monitoring. Inborn errors of metabolism, like MSUD, should be considered, even if universally screened, as delayed diagnosis can result in prolonged hospitalization and significant morbidity.