Table 2.

Genetic defects in thiamine transport and metabolism.

Deficiency	Gene Mutation	Disease	Symptoms
THTR1	SLC19A2	Thiamine-responsive megaloblastic anemia (TRMA, also known as the Rogger syndrome)	Megaloblastic anemia, diabetes mellitus, hearing loss
THTR2	SLC19A3	Biotin-thiamine responsive encephalopathy	Episodic encephalopathy, gait ataxia, seizures, bulbar dysfunction
Mitochondrial TPP transporter	SLC25A19	Amish lethal microcephaly	Severe congenital microencephaly, death within the first year, episodic encephalopathy
TPK1	TPK1 gene	Thiamine metabolism dysfunction syndrome 5	Episodic encephalopathy, ataxia, dystonia and spasticity, loss of ability to walk
BCKDH	DBT gene	Maple syrup urine disease (MSUD)	Impaired mental development, seizures, lethargy, progressive neurodegeneration, maple syrup odor in the cerumen and the urine