MTHFR and neurodegenerative syndrome due to cerebral folate transport deficiency: Cerebral folate deficiency (CFD), caused by folate receptor autoantibodies or germline mutations such as in FOLR1 (folate receptor alpha), SLC46A1 (solute carrier family 46 member 1) or MTHFR genes, is manifested in neurological impairments and shows deficiency of 5-methyl-THF in the cerebrospinal fluid (CSF) in the presence of low or undefined peripheral folate levels (42, 43).