Vitamin B12 metabolism in multiple sclerosis.

We have previously described 10 patients with multiple sclerosis (MS) and unusual vitamin B12 deficiency. We have therefore studied vitamin B12 metabolism in 29 consecutive cases of MS, 17 neurological controls, and 31 normal subjects. Patients with MS had significantly lower serum vitamin B12 levels and significantly higher unsaturated R-binder capacities than neurological and normal controls, and they were significantly macrocytic compared with normal controls. Nine patients with MS had serum vitamin B12 levels less than 147 pmol/L and, in the absence of anemia, this subgroup was significantly macrocytic and had significantly lower red blood cell folate levels than neurological and normal controls. Nine patients with MS had raised plasma unsaturated R-binder capacities, including three patients with very high values. There is a significant association between MS and disturbed vitamin B12 metabolism. Vitamin B12 deficiency should always be looked for in patients with MS. The cause of the vitamin B12 disorder and the nature of the overlap with MS deserve further investigation. Coexisting vitamin B12 deficiency might aggravate MS or impair recovery from MS.