Recessive variants can induce well-defined phenotypes; SLC19A2 induces thiamine responsive megaloblastic anemia or Roger’s syndrome; SLC19A3 produces biotin thiamine responsive basal ganglia disease and Leigh syndrome; TPK1 causes Leigh syndrome; and SLC25A19 causes Amish microcephaly and episodic encephalopathy with progressive polyneuropathy[298–300]. The gene discussed is TPK1; the disease is microcephaly.