Maple Syrup Urine Disease Masquerading as Urea Cycle Disorder: A Tale of Two Clinical Mimics

Maple syrup urine disease, an inherited disorder of metabolism, is characterised by deficient activity of the branched-chain alpha-keto acid dehydrogenase complex (BCKAD) enzyme, resulting in an accumulation of branched-chain amino acids. While it is classically diagnosed by the means of a neonatal screening panel, it can sometimes remain undetected. In such cases, maple syrup urine disease is noted to elicit a constellation of clinical symptoms characterised by a plethora of neurological and respiratory impairments. A prompt diagnosis and management of the disease therefore remains imperative. Due to the remarkable semblance in the clinical symptoms elicited by maple syrup urine disease and urea cycle disorders, both the ailments should be considered in the list of differential diagnosis in patients presenting with elevated serum ammonia levels in the context of the overarching clinical picture. We chronicle the case of a 25-day-old neonate who presented with unabated seizures. An initial diagnosis of a urea cycle disorder was suspected; however, further diagnostic workup divulged an underlying diagnosis of maple syrup urine disease.

Keywords: inborn errors of metabolism; maple syrup urine disease; urea cycle disorder.