Mutations in this gene cause biotin-thiamine-responsive basal ganglia disease (BTBGD); a recessive disorder manifesting in childhood, which – if untreated – progresses to chronic encephalopathy, dystonia, quadriparesis, and eventually death.[9] Patients with BTBGD exhibit bilateral necrosis in the head of the caudate nucleus and in the putamen. The progression of symptoms is paused by the lifelong administration of both high doses of biotin and thiamine. The residual symptoms vary widely between individuals, often encompassing paraparesis, mild mental retardation, or dystonia. Administration of thiamine by itself is ineffective in the treatment of this disorder. Experiments have failed to show that this protein can transport biotin, but the expression of the transporter is starkly reduced with even just latent biotin deficiency. Mutations in this gene also cause a Wernicke's-like encephalopathy.[5]
