Weakness and fatigue are common symptoms of Vitamin B12 deficiency
Weakness and fatigue are common symptoms of vitamin B12 deficiency.
They occur because your body
doesn't have enough vitamin B12 to make healthy red blood cells, which
transport oxygen throughout your body.
As a result, you are unable
to efficiently transport oxygen to your body's cells, making you feel tired and weak.
Vitamin B12 deficiency can
cause damage to your nerves and can affect memory and thinking.
The MCV is a measure of the average volume, or size, of a
single RBC. [Red Blood Cell]
Cell size is indicated by the terms "normocytic",
"microcytic", and "macrocytic".
Normal MCV values vary according to age and gender. When the MCV value is increased, the RBC is
said to be abnormally large, or macrocytic.
This is most frequently seen in vitamin B12 or folic acid
deficiency.
Vitamin B12 deficiency is a cause of macrocytosis. Because
DNA synthesis requires cyanocobalamin (vitamin B12) as a cofactor, a deficiency
of the B12 vitamin leads to decreased DNA synthesis in the erythrocyte, thus
resulting in macrocytosis.
Macrocytosis, or megaloblastic anemia, is a blood condition
characterized by insufficient and unusually large red blood cells.
Specific Causes of Macrocytosis
VITAMIN B12 DEFICIENCY
Vitamin B12 is absorbed by the ileum when it is bound by intrinsic factor, which is produced by the parietal cells of the gastric mucosa.
In pernicious anemia, the loss of parietal cells leads to insufficient absorption of vitamin B12, which then leads to vitamin B12 deficiency over time.
Pernicious anemia is most commonly caused by auto-immune atrophic gastritis, in which autoantibodies are directed against parietal cells and intrinsic factor.
Less commonly, pernicious anemia can be caused by nonautoimmune gastritis secondary to H. pylori infections and Zollinger-Ellison syndrome.
Patients with vitamin B12 deficiency may describe paresthesias related to peripheral neuropathy, poor or strict vegan diet, lack of socioeconomic resources, bowel-related symptoms (including diarrhea), or a history of bowel surgery for weight loss.
Findings on physical examination may include neurologic signs such as ataxia, decreased proprioception, and vibratory sensation.
Patients may also have poor dentition or nonspecific oral stomatitis or glossitis.
Because pregnant women take folic acid routinely in prenatal vitamins, macrocytic anemia is much less common during pregnancy.
Consider nitrous oxide abuse in at-risk populations, because nitrous oxide inactivates vitamin B12 through oxidation.
Other uncommon causes include Diphyllobothrium latum (i.e., fish tapeworm) infection or inherited disorders of cobalamin metabolism, including Imerslund syndrome (a congenital vitamin B12 malabsorption associated with proteinuria).
Only 10 percent of persons with vitamin B12 deficiency are actually anemic.
