Movement disorders associated with thiamine pyrophosphokinase deficiency: Intrafamilial variability in the phenotype

• Thiamine pyrophosphokinase deficiency due to TPK1 mutations typically presents as a childhood disorder with episodic encephalopathy with psychomotor retardation , but some patients can survive into adulthood with disabling movement disorder . • There are intrafamilial variability in the phenotype associated with TPK deficiency. • Adult neurologists should be aware of this genetic etiology as early recognition might possibly lead to improvement with thiamine in some patients.