Experimental autoimmune encephalomyelitis (EAE) is an autoimmune disease believed to be a model for the human disease multiple sclerosis (MS). Induced by immunizing B10.PL mice with myelin basic protein (MBP), EAE was completely prevented by the administration of 1,25-dihydroxyvitaminD3 [1,25-(OH)2D3]. 1,25-(OH)2D3 could also prevent the progression of EAE when administered at the appearance of the first disability symptoms. Withdrawal of 1,25-(OH)2D3 resulted in a resumption of the progression of EAE. Thus, the block by 1,25-(OH)2D3 is reversible.

Of 27 Asians with a megaloblastic bone marrow, 22 (81%) had nutritional deficiency of vitamin B12 (NMA), while five (19%) had true pernicious anaemia (PA). All the patients were Hindu vegetarians except for a single Muslim who had PA. Dietary intakes of calories, protein, iron, vitamin B12 and folate were below the recommended level in both groups. The PA group had lower levels of serum B12 and higher levels of serum folate than the NMA group.

138 Indian patients with megaloblastic haemopoiesis were studied. All were lifelong vegetarians. The diagnosis was nutritional cobalamin deficiency in 95 and pernicious anaemia in 20; only 4 patients had folate deficiency. A third had intestinal malabsorption, 20 had features of osteomalacia, and 87 were iron deficient. Tuberculosis was diagnosed in 17. Cobalamin deficiency may have contributed to these complications via intestinal malabsorption and impaired bacterial killing of phagocytosed bacilli by cobalamin-deficient macrophages.

Megaloblastic anaemia in infancy is uncommon in western countries. We describe a case of an exclusively breast-fed monozygous twin with severe vitamin B12 deficiency with haematologic and neurologic abnormalities. Treatment with vitamin B12 resulted in a rapid haematological and clinical improvement.