Multiple Sclerosis Associated With Vitamin B12 Deficiency

• We describe 10 patients with a previously unreported, to our knowledge, association of multiple sclerosis and unusual vitamin B₁₂ deficiency. The clinical features and the age at presentation were typical of multiple sclerosis, with eight cases occurring before age 40 years, which is a rare age for vitamin B₁₂ deficiency. Nine patients had hematologic abnormalities, but only two were anemic. All six patients examined had low erythrocyte cobalamin levels. Only two patients had pernicious anemia; in the remaining patients the vitamin B₁₂ deficiency was unexplained. A vitamin B₁₂ binding and/or transport is suspected. The nature of the association of multiple sclerosis and vitamin B₁₂ deficiency is unclear but is likely to be more than coincidental. Further studies of vitamin B₁₂ metabolism, binding, and transport in multiple sclerosis are indicated, as these cases may offer a clue to the understanding of a still mysterious neurologic disorder.