MTHFR deficiency (OMIM#607093) appears typically in the neonatal period, with severe neurological signs, recurrent apnea, microcephaly, encephalopathy, hypotonia, and seizures, although late onset forms of MTHFR deficiency showing seizures, cognitive impairment, neuropathy and psychiatric disorder are also known [8,9,10,11]. This evidence concerns the gene MTHFR and hyperinsulinemic hypoglycemia, familial, 4.