Immunodeficiency and inborn disorders of vitamin B12 and folate metabolism

PURPOSE OF REVIEW

Immune dysfunction, including severe combined immunodeficiency, has been described in genetic disorders affecting the metabolism of the vitamins cobalamin (vitamin B12) and folate. We have reviewed reports of clinical findings in patients with a number of inborn errors of cobalamin or folate metabolism, specifically looking for immune problems.

RECENT FINDINGS

There is little evidence that immune function is affected in most of the disorders. Exceptions are Imerslund-Gräsbeck syndrome and hereditary folate malabsorption (affecting intestinal absorption of cobalamin and folate, respectively), transcobalamin deficiency (affecting transport of cobalamin in blood and cellular cobalamin uptake), and methylenetetrahydrofolate dehydrogenase 1 deficiency (catalyzing cytoplasmic interconversion of reduced folate coenzyme derivatives).

SUMMARY

Although some inborn errors of cobalamin or folate can be associated with immune dysfunction, the degree and type of immune dysfunction vary with no obvious pattern.

[IMERSLUND-GRÄSBECK SYNDROME CONGENITAL FORM OF VITAMIN B12 DEFICIENCY ANEMIA]

Normal red blood cells maturation depends on many different hematological factors, including vitamin (vit.) B12. Megaloblastic anemias are basically caused by vit. B12 deficiency. In childhood the deficiency of this vitamin is extremely rare. The article captures findings of observation of the patient with rare form congenital vit. B12 deficiency anemia - Imerslund-Gräsbeck syndrome. The disease is characterized with selective intestinal malabsorption of vit. B12 and permanent proteinuria, without sings of kidney disease. The diagnosis was confirmed by our team in early childhood and based on the history, clinical and paraclinical data. After two weeks of specific treatment with vit. B12 , complete clinical - hematological remission was achieved. Treatment includes lifelong vit. B12 injections once per month. Cathamnesic observation for 18 months revealed that the patient is in remission, but there was continued macrocytosis of red blood cells and mild proteinuria. The presented case is interesting as a rare case of megaloblastic anemia caused by vit. B12 deficiency in childhood. Such patients often treated under different diagnosis. In such cases early diagnosis, treatment and prevention are crucial for the good prognosis.

Linkage analysis of a large inbred family with congenital megaloblastic anemia

OBJECTIVE

Megaloblastic anemia during infancy and early childhood often reflects a hereditary disorder of cobalamin's absorption, transport, or intracellular metabolism. There are 3 well defined autosomal recessive syndromes manifesting with megaloblastic anemia due to defects in cobalamin absorption or transport, namely congenital pernicious anemia, Imerslund-Grasbeck syndrome and Transcobalamin II deficiency. The genes responsible for the 3 disorders are gene intrinsic factor (GIF), MGA1 and TCN2, as well as the gene for Transcobalamin I, TCN1 are mapped or cloned, or both.

METHODS

We describe the clinical picture of 7 patients from 3 sibships, belong to one large inbred family who presented with megaloblastic anemia during infancy. The mode of inheritance follows an autosomal recessive pattern and the syndrome was completely reversed by parentral vitamin B12 therapy. The ascertainment of the family was carried out in 1998 in the Princess Rhama Children's Hospital, which is affiliated with Jordan University of Science and Technology, Jordan. We performed linkage analysis in this family for genes or regions involved in the above mentioned disorders.

RESULTS

The genes implicated in the etiology of the previously mentioned disorders were excluded from being responsible for the disorder in this family.

CONCLUSION

The exclusion of the involvement of GIF, MGA1, TCN1 and TCN2 in this family suggests that another gene and its product, involved in cobalamin absorption or transport, remains to be identified. A genome-wide search of the gene implicated in this family may give some insight on that gene, and its function.

[Congenital megaloblastic anemia in a 22-month-old boy]

A 22-month old boy with the congenital form of megaloblastic anaemia is presented. The child was admitted to hospital with moderate-to-severe hematological and neurological symptoms. Very low serum vitamin B12 concentration and normal gastric secretion were determined. A dramatic recovery after intramuscular injections with vitamin B12 was observed.

Combined congenital deficiencies of intrinsic factor and R binder

Coexisting deficiencies of both intrinsic factor (IF) and R binder were identified in an Algerian boy who presented with severe megaloblastic anemia, growth retardation, and neurologic dysfunction with typical features of subacute combined degeneration of the spinal cord. The anemia responded completely to cyanocobalamin and folic acid. IF was absent from gastric juice, but acid secretion and gastric mucosa were normal. R binders were absent from gastric juices as well as from serum, saliva, and polymorphonuclear leukocytes. The patient's father exhibited absence of R binder in his serum with a low serum vitamin B12 level and was asymptomatic. This unique case of simultaneous IF and R binder deficiencies suggests a genetic association between these two functionally and immunologically dissimilar, but structurally close vitamin B12-binding proteins.

[Congenital intrinsic factor deficiency. Apropos of 3 cases in a sibship]

Three familial cases of congenital intrinsic factor deficiency are reported: the stress is put on the interest of gastric investigations and especially of the quantity of intrinsic factor in the gastric juice when investigating megaloblastic anemia due to vitamin B12 deficiency. The study of the level of intrinsic factor in the gastric juice is proposed as a test for identifying carriers.

Congenital folate malabsorption

A Turkish girl presented with a history of fever, diarrhoea, convulsions, recurrent infections and failure to thrive from the age of 5 months. Megaloblastic anaemia was present and profound folate deficiency was evidenced in plasma and in CSF. Treatment with oral folic acid cured the anaemia, diarrhoea and infections but failed to prevent convulsions and the appearance of mental retardation and cerebral calcifications. Loading tests with folic acid and its derivatives led to the conclusion that the folate deficiency was caused by a defect in folate transport both across the gut and the blood-brain barrier. Low plasma concentrations of methionine prompted a therapeutic trial with methionine associated with vitamin B12 and folic acid that spectacularly improved the convulsions.

[Coexistence of late spondyloepiphyseal dysplasia and congenital megaloblastic anemia with proteinuria in the same family]

A case of spondyloepiphyseal dysplasia tarda was noted in a dwarf (130 cm tall) 18 years old boy associated with congenital megaloblastic anemia and proteinuria. His two sisters and a cousin are also suffering from similar hematologic disorder. One of his brothers, 145 cm tall, is also involved by spondyloepiphyseal dysplasia, but there is no known hematologic abnormalities. Review of family history revealed that two aunts from mother's side were deceased in adulthood following a chronic anemic disease. The findings in this anemia are compatible with Imerslund-Grâsbech syndrome and coexistence of these two rare genetic disorders in a single family has not been reported previously.

[Congenital malabsorption of vitamin B12 (Imerslund's syndrome) in a premature girl with Down's syndrome (author's transl)]

A baby girl, born prematurely and with Down's syndrome, is hospitalized at the age of 51 days for a megaloblastic anemia. The anemia was caused by a selective malabsorption of vitamin B12 (Imerslund's syndrome), even in presence of intrinsic factor. The pathogenesis of different causes of vitamin B12 deficiency is discussed and the favourable development of this case after four years of treatment is shown.

Thiamine-responsive megaloblastic anemia, sensorineural deafness, and diabetes mellitus: A new syndrome?

A 6-year-old girl is described who has congenital megaloblastic anemia which completely responded only to pharmacologic doses of thiamine. Relapse was observed twice when the drug was discontinued. The reintroduction of thiamine caused a prompt reticulocytosis and a rise in hemoglobin concentration. Other abnormalities included latent diabetes mellitus, sensorineural deafness, and "situs inversus totalis." Her parents are first cousins, both with partial deafness. Her father has an abnormal oral glucose tolerance test. A single similar case has been reported; the combination of almost the same anomalies seems to represent a newly recognized syndrome. This case reinforces the proposal that thiamine has a role in hematopoesis.

Dihydrofolate reductase deficiency causing megaloblastic anemia in two families

To determine the cause of severe megaloblastosis detected at birth and at four weeks in two unrelated infants their bone marrow and liver cells were studied. Both patients had abnormal deoxyuridine suppression tests, corrected to normal by 5-formyl tetrahydrofolic acid. Liver-cell homogenate from one patient had a previously undetectable level of dihydrofolate reductase restored to normal by high cation concentration in the assay. Activity of the liver-cell homogenate from the other patient, which was one quarter of the normal level, was restored to only half normal activity by high cation concentration. Dihydrofolic acid reductase deficiency prevents this conversion of folic acid to tetrahydrofolic acid; the enzyme activity appears to differ in each patient. A satisfactory clinical response in both patients followed parenteral therapy with 5-formyl tetrahydrofolic acid. One sibling in each family died of a similar illness. Autosomal recessive inheritance is probable.

[Congenital aplastic anemia, type I]

Case report of a 7 year old girl, anaemic since birth. The anaemia, of variable intensity, is associated with a moderate reticulocytosis. Bone marrow films, show a marked erythroblastosis with conspicuous morphological abnormalities and internuclear chromatin bridges. The erythrocinetic pattern is that of ineffective erythropoiesis. The morphologic features are those of Heimpel and Wendt's type I congenital dyserythropoiesis. The erythrocytes are lysed by some acidified sera, thus showing a membrane anomaly which is unusual in type I. However the characteristics of the lysis are different from those of type II (HEMPAS) erythrocytes.