Arch Dis Child. 2002 Jul; 87(1): 75-6.

Nature and nurture in vitamin B12 deficiency.

Zschocke J, Schindler S, Hoffmann GF, Albani M.

Institute of Human Genetics, Heidelberg University, Germany. kawahara@pedsurg.med.osaka-u.ac.jp

We report on a child in whom severe nutritional vitamin B12 deficiency was exacerbated by a genetic impairment of the folate cycle, causing reduced CSF concentrations of the methyl group donor 5-methyltetrahydrofolate. Some patients with vitamin B12 deficiency may benefit from high dose folic acid supplementation, even if plasma concentrations are high.