Intermittent Maple Syrup Urine Disease Presenting With Chronic Demyelinating Polyneuropathy: A Genetically Confirmed DBT-Related Case

Background and aims: Maple syrup urine disease (MSUD) is an inherited disorder of branched-chain amino acid metabolism caused by deficiency of the branched-chain α-keto acid dehydrogenase complex. Neurological manifestations predominantly involve the central nervous system, whereas peripheral nervous system involvement has been rarely reported.

Results

We report a genetically confirmed case of intermittent MSUD caused by compound heterozygous pathogenic variants in DBT in a female patient who developed recurrent ataxic episodes beginning in early childhood, followed by acute ascending weakness during metabolic decompensation at 12 years of age. Initially suspected to have Guillain-Barré syndrome, subsequent biochemical and molecular investigations established the diagnosis of MSUD. Five years later, despite good metabolic control and substantial functional recovery, follow-up nerve conduction studies, and electromyography demonstrated a chronic demyelinating sensorimotor polyneuropathy. Clinical examination additionally revealed bilateral pes cavus and persistent mild distal lower-limb weakness.