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January 5, 1990

Acquired Immunodeficiency Syndrome and the Nervous System

Author Affiliations

Columbus, Ohio

Columbus, Ohio

JAMA. 1990;263(1):37. doi:10.1001/jama.1990.03440010035019

To the Editor.—  The workup described by Dalakas et al1 for their patient with neuropathy and dementia was inadequate. B12 deficiency is a significant cause of the neuropathy they describe in the absence of hematologic abnormalities and with normal B12 levels.2 In the fruit bat, the only animal model of B12 deficiency, changes occur in fatty acid metabolism and plasma membranes.3Humans are the only animals that become B12 deficient, resulting in hematologic effects.4 This could explain why animals do not develop acquired immunodeficiency syndrome even though the virus replicates in monkeys. B12 is associated with impaired cellular immunity as evidenced by vegetarians, who have an increased incidence of tuberculosis.4 Cadmium, unlike lead and mercury, does not become methylated by B12 but instead binds to the cobalt, destroying the function of the cofactor. The effects found in brain with