Conditions Associated with Vitamin B,2 Deficiency

Clinical Conditions Associated with Vitamin B]2 Deficiency 

Examination of the bone marrow, although important, will only confirm that the hemopoiesis is megaloblastic. A deficiency of folic acid will also cause a megaloblastic anemia and it is not possible to identify the cause on the basis of morphology. A serum assay of both vitamins will usually indicate which is responsible. If the patient is vitamin B12 deficient, the next step is to carry out a vitamin B12 absorption test to confirm that the deficiency is due to a lack of intrinsic factor. Preferably this should not be done until the patient s vitamin B12 and hemoglobin levels have returned to normal, since the gastric and intestinal cells are also affected by a lack of vitamin B12 aborption may be less than optimal if it is attempted too early. Patients with pernicious anemia also have a histamine-fast achlorhydria and gastric atrophy. The disease appears to have an autoimmune basis and antibodies to intrinsic factor can be demonstrated in the serum of more than half of affected patients. 

In a study of peripheral nerve involvement in 20 patients with untreated penicious anemia, Cox-Klazinga and Endtz (C17) found 13 to have signs of peripheral nerve dysfunction with reduced conduction velocities. Interestingly, 16 of these patients were also found to have reduced blood thiamin levels. Clinical signs of peripheral nerve involvement were reported by Pallis and Lewis (P4) to be common in patients with untreated pernicious 

In a study of vitamin B12 levels in 835 consecutive psychiatric patients, Elsborg et al. (E6) found a reduced serum concentration in 10%. Of these 1 patient had pernicious anemia, 7 were postgastrectomy, and 1 had previously had a small bowel resection the remaining 72 patients were considered to have a nutritional deficiency. 

This condition has often been referred to in the past as juvenile pernicious anemia but it appears to be a quite separate entity. Confusion probably arose because there is a deficiency of intrinsic factor resulting in vitamin B12 malabsorption in both conditions. However, it differs from the disease in adults in that free acid is present in the gastric secretion (A8,L3,M5), the gastric mucosa is usually normal, and antibodies to intrinsic factor are not a feature. Megaloblastic anemia usually develops during the first 2 years of life but this depends on the amount of residual intrinsic factor available, and 

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