PubMed · 53468
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M R Boarder. 1975-11-15. Letter: The methylfolate trap.. https://doi.org/10.1016/s0140-6736(75)90400-6
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Transcobalamin II(TC II) is an essential transport protein for vitamin B12 in blood. TC II can be split up into isoproteins by polyacrylamide gel electrophoresis. Family studies are compatible with a genetic polymorphism of TC II and a five allele system. Screening of TC II isoprotein patterns in about 1000 individuals yielded two unusual TC II variants: The first case was a black female with severe megaloblastic anemia since infancy. Her TC II was elevated and bound B12, but displayed markedly diminished functional capacity to transfer radioactive cyanocobalamin in cellular systems. Comparison of this patient's TC II isoprotein pattern with known variants showed a distinct difference in electrophoretic mobility, indicating the presence of a sixth allele. The second patient, also presenting with pernicious anemia-like symptoms, was found to possess an unusual TC II variant with reduced TC II serum levels. Corresponding variants were also observed in the patient's asymptomatic children. Thus, abnormal TC II variants probably causing megaloblastic anemias both correlated with unusual isoprotein patterns.
A case of the exclusively breast-fed infant of a vegetarian mother is reported. Neurological deterioration commenced between three and six months of age, and progressed to a comatose premoribund state by the age of nine months. Investigations revealed a mild nutritional vitamin B12 deficiency in the mother, and a very severe nutritional B12 deficiency in the infant, with severe megaloblastic anaemia. Treatment of the infant with vitamin B12 resulted in a rapid clinical and haematological improvement, but neurological recovery was incomplete. Evidence is presented that dietary B12 deficiency was the sole cause of the infant's deterioration, and the literature relating to the condition is reviewed. It is recommended that all strict vegetarians (vegans), especially women in the child-bearing age group, take vitamin B12 supplements.