Carbamazepine responsive episodic dystonia and hallucination due to pyruvate dehydrogenase E2 (DLAT) gene mutation

Pyruvate Dehydrogenase (PDH) E2 deficiency due to Dihydrolipoamide acetyltransferase (DLAT) mutations is a very rare condition with only nine reported cases to date. We describe a 15-year-old girl with mild intellectual disability, paroxysmal dystonia and bilateral basal ganglia signal abnormalities on brain magnetic resonance imaging (MRI). Additionally, neurophysiological, imaging, metabolic and exome sequencing studies were performed. Routine metabolite testing, and GLUT1 and PRRT2 mutation analysis were negative. A repeat brain MRI revealed 'Eye-of-the-tiger-sign'. Exome sequencing identified homozygous valine to glycine alteration at amino acid position 157 in the DLAT gene. Bioinformatic and family analyses indicated that the alteration was likely pathogenic. Patient's dystonia was responsive to low-dose carbamazepine. On weaning carbamazepine, patient developed hallucinations which resolved after carbamazepine was restarted. PDH E2 deficiency due to DLAT mutation has a more benign course compared to common forms of PDH E1 deficiency due to X-linked PDHA1 mutations. All known cases of PDH E2 deficiency due to DLAT mutations share the features of episodic dystonia and intellectual disability. Our patient's dystonia and hallucinations responded well to low-dose carbamazepine.