Teaching NeuroImages: Subacute encephalopathy in a young woman with THTR2 gene mutation.

A 21-year-old woman presented with coma after 5 days of fever, gait ataxia, and somnolence. Brain MRI showed lesions in medial thalami, caudate heads, and periaqueductal region (figure). Hyperlactatemia was present; serum thiamine levels were normal. Thiamine IM 600 mg daily led to complete recovery within 3 days. Sequencing analysis of thiamine transporter 2 (THTR2) gene revealed a base deletion, at homozygote state, in intron 3 in position c.980-4 upstream at donor/acceptor site of exon 4, predicted by computational algorithms to be deleterious. In young adults, THTR2 dysfunction may foster subacute encephalopathy with typical radiologic manifestations that is promptly responsive to thiamine administration.