Late-Onset Malonic Aciduria Mimicking Juvenile Myoclonic Epilepsy: Electroclinical Recovery after Metabolic Therapy

Malonic aciduria, caused by malonyl-CoA decarboxylase ( MLYCD ) deficiency, is a rare disorder of mitochondrial fatty-acid metabolism. Although the disease usually presents in infancy with cardiomyopathy and metabolic disturbances, late-onset forms with predominant neurological manifestations have been increasingly recognized. We report a 17-year-old girl initially diagnosed with juvenile myoclonic epilepsy who presented with absence seizures, myoclonic jerks, tremor, and prominent motor tics. Electroencephalography (EEG) demonstrated generalized 3–4 Hz spike–wave discharges with photic sensitivity. Metabolic investigations revealed elevated malonylcarnitine and urinary malonic acid levels. Whole-exome sequencing identified a homozygous MLYCD c.1310C>T (p.Ala437Val) variant, confirming the diagnosis of malonic aciduria. Treatment with levocarnitine, dietary modification, and lamotrigine resulted in complete clinical recovery and normalization of EEG findings within 1 year. This case highlights that metabolic disorders such as malonic aciduria may mimic idiopathic generalized epilepsy and should be considered in patients with atypical clinical features.