The primary immunodeficiency disorders reflect abnormalities in the development and maturation of cells of the immune system. These defects result in an increased susceptibility to infection; recurrent pyogenic infections occur with defects of humoral immunity, and opportunistic infections with defects of cell-mediated immunity. These two broad categories of illness correspond roughly to defects in the two principal types of immunocompetent cells, B lymphocytes and T lymphocytes. Defective development of B cells results in abnormalities in humoral immunity, whereas defects in the development of T cells cause problems with cellular immunity. When pathogens are taken up by macrophages or dendritic cells, . . .

The Primary Immunodeficiencies

We studied a six-month-old infant with severe megaloblastic anemia, coma and hyperpigmentation of the extremities. He was found to have methylmalonic aciduria (79 mumol per milligram of creatinine) and homocystinuria (0.85 mumol per milligram of creatinine). Additional biochemical abnormalities included cystathioninuria, glycinuria, methylcitric aciduria, 3-hydroxypropionic aciduria and formic aciduria. The concentration of vitamin B12 in the serum was 20 pg per milliliter. This severe nutritional deficiency was a consequence of inadequate intake, for the infant was exclusively breast-fed by a strictly vegetarian mother who manifested methylmalonic aciduria. Our observations emphasize the importance of educating strict vegetarians about the deficiency of vitamin B12 in their diets and the importance of vitamin B12 supplementation.

https://www.nejm.org/doi/pdf/10.1056/NEJM197808172990701

A Syndrome of Methylmalonic Aciduria, Homocystinuria, Megaloblastic Anemia and Neurologic Abnormalities in a Vitamin B12-Deficient Breast-Fed Infant of a Strict Vegetarian

Anemia is probably the commonest effect of nutritional deficiency in human beings and has certainly been the most extensively studied. Iron deficiency is widely recognized as the most important cause of anemia in the world (Finch, 1969; Beaton, 1974).

The Hematopoietic System

Multiple biotin-dependent carboxylase deficiencies associated with defects in T-cell and B-cell immunity

It is generally assumed that vitamin B12 deficiency only occurs during pregnancy and lactation in women who have consumed no animal products for a substantial period of time However, recently it has emerged that pregnant women who have been strict vegetarians for only a few years, and even omnivores who consume low amounts of animal products, are more likely to become vitamin B12 deficient during pregnancy and lactation, to give birth to an infant who develops clinical or biochemical signs of B12 deficiency, and/or to have low levels of this vitamin in their breast milk Also, there is recent evidence that vitamin B12 deficiency may be more prevalent in women and infants in some developing countries than formerly appreciated In view of the potential for vitamin B12 deficiency to cause permanent neurological damage, it is important to understand the relationships between maternal intake and metabolism of vitamin B12 during pregnancy and lactation, and their impact on the mother, fetus, neonate, and secretion of the vitamin in breast milk

D. Vischer

Papers

Hereditary transcobalamin II deficiency: clinical findings in a new family.

[Severe coagulopathy caused by immunological inhibitors of factors, II, V, VII and X].