Vitamin B12 deficiency and MS share pathological changes and B12-dependent methylation and MTHFR have been suspected to play a role in MS for decades.32 Homocysteine levels in the blood and cerebrospinal fluid of MS patients have been found to be elevated in some studies,33–35 but not in others.36, 37 A recent study found different concentrations of methionine metabolites in brains of MS patients compared to brains of controls and suggested an effect on mitochondria and neuronal energetics.38 The gene discussed is MTHFR; the disease is myeloid sarcoma.