Anemia can be classified into 3 types according to the red cell morphology. Vitamin deficiency anemia, which is a type of macrocytic anemia.
Vitamin deficiency is not the only cause for macrocytic anemia. Other causes include liver disease, alcoholism, hypothyroidism, COAD etc.
Pathophysiology
There are 2 vitamins which, in their deficient state can cause anemia. They are vitamin B12 and folate.
Both these vitamins are essential in the process of mitosis through which red blood cells are produced in the bone marrow.
Before any cell division, replication of DNA needs to take place.
For DNA replication, ample amounts of free deoxyribonucleotides, are necessary.
Folate, or rather methylene tetrahydrofolate, which is an active form of folate, acts as a co enzyme in the process of producing dTMP which is one of the essential nucleotides for DNA synthesis.
B12 is required to synthesize more methylene tetrahydrofolate from one of its other forms, methyl tetrahydrofolate.
Both folate and vitamin B12 plays a part in red blood cell production.
Hence a deficiency in any of these will reduce the efficiency of erythropoiesis, resulting in anemia.
Causes
A vitamin deficiency may occur due to several reasons. Nutritional deficiency is a major cause for both folate and vitamin B12 deficiency.
Vitamin BB12in food binds to a glycoprotein called intrinsic factor which is secreted by the stomach.
This facilitates its absorption which mainly occurs in the ileum.
Hence gastric causes like pernicious anemia which is a term used to describe a intrinsic factor deficiency and gastrectomy, as well as ileal causes like ileal resections, blind loops and presence of fish tape worms in the ileum may cause vitamin B12 deficiency.
Folate on the other hand, is absorbed in the jejunum mainly.
Hence inflammatory conditions in the jejunum such as coeliac disease can affect folate absorption.
Folate deficiency may also occur in states of higher demand such as pregnancy and myeloproliferative disease.
Patients with vitamin deficiency anemia will also present with the common anemic symptoms such as pallor, fatigue, shortness of breath etc.
They will also have glossitis and angular stomatitis which will be evident upon examination.
Vitamin B12 deficiency, but not folate deficiency, will cause peripheral neuropathy and a condition called SACD (subacute combined degeneration) of the spinal cord.
Laboratory Investigations
A full blood count will show a decrease in the hemoglobin level and hematocrit. The characteristic feature will be the increase in MCV.
It will be more than 96 flights and most of the time even higher than 125 fl.
As suggested by the FBC, the blood picture will also show macrocytes.
There will also be a reduction in neutrophil and platelet numbers due to ineffective production.
The bone marrow will be hypercellular and have large erythroblasts.
Hence these kinds of macrocytic anemias are also called megaloblastic anemias.
Several specific tests are available to establish the exact cause.
These include serum B12 assay and Schilling test for B12 deficiency and red cell folate assay for folate deficiency.
Treatment
Vitamin deficiency anemias are treated by supplementation of the deficient vitamin.
Folic acid is given orally and hydroxocobalamin (vitamin B12) as an IM injection according to the need.
However, we should start both vitamins if we are unsure of the cause as giving folate only may worsen the neuropathy in B12 deficiency.
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