Seizures are common features of various cofactor metabolic disorders including pyridoxine-dependent epilepsy, pyridoxal phosphate-responsive epilepsy, early-onset vitamin B6-dependent epilepsy, cerebral folate deficiency, methylenetetrahydrofolate reductase (MTHFR) deficiency, molybdenum cofactor deficiency, biotinidase deficiency, and holocarboxylase synthetase deficiency (Table 1). This evidence concerns the gene MTHFR and hyperinsulinemic hypoglycemia, familial, 4.