Out of 30 patients with severe homocystinuria due to MTHFR deficiency, Huemer et al. found 15 with brain atrophy, 13 with Leukodystrophy/dysplasia of the brain myelin sheath, and 9 with ventricular enlargement/hydrocephalus in their MRI examination [1]. Here, MTHFR is linked to hyperinsulinemic hypoglycemia, familial, 4.