The etiology of multiple sclerosis is unknown, although it is widely believed to be associated with a viral or immunologic cause. Vitam B12 deficiency, although associated with several neurologic complications, has not previously been reported in association with multiple sclerosis. However, Reyolds* and colleagues report 10 cases in Great Britain in which an unusual vitamin B12 deficiency occured in association with multiple sclerosis.

The 10 patients (seven women and three men) ranged in age from 27 to 51 years at the onset of neurologic disease, and all presented with the typical clinical features of multiple sclerosis. Magnetic resonance imaging performed in seven of the patients revealed multiple lesions in the white matter consistent with multiple sclerosis. Vitamin B12 deficiency, although unusual in patients under 40, was present before this age in eight of the patients.

Results of electromyograms revealed no peripheral neuropathy, although this is the most common neurologic manifestation of vitamin B12 deficiency.

Nine of the patients had serum vitamin B12 levels below 203 pg per mL (150 pmol per L). The cause of the vitamin deficiency was unknown in most of the patients. Only two of the patients were anemic, and only two of the patients had pernicious anemia. None of the patients had gastrointestinal disease or had previously undergone gastrectomy. Eight patients had macrocytosis.

Large-scale studies conducted in the early 1960s did not demonstrate an association between multiple sclerosis and low levels vitamin B12 in serum and cerebrospinal fluid. However, the authors conclude that there may be an association between vitamin B12 deficiency and multiple sclerosis that is more than coincidental.

Further studies of vitamin B12 metabolism, binding and transport in patients with multiple sclerosis are indicated.