I have pernicious anemia (PI). I have tried to find out more about it, but I have been unsuccessful. About four years after diagnosis I found out that people with this are more suceptible to stomach cancer. I would like to find out if there are any other things I am not yet aware of.
Pernicious anemia was so named because of the inexorable downhill course of people who had it before the discovery that injections of liver extract could cure the disease. It is now known to be due to a deficiency of Vitamin B12, which is necessary for the production of blood cells, the maintenance of nerves, both in the central nervous system and in peripheral nerves, and the maintenance of cells lining the gastrointestinal tract.
Pernicious anemia is a megaloblastic anemia, meaning that the red cells that are produced are larger than normal. There are several other kinds of megaloblastic anemia, but for practical purposes the only one seen in this country is due to folic acid deficiency, mostly in alcoholics.
Vitamin B12 is only available in our diet in foods of animal origin. Humans are one of the few mammals that cannot make Vitamin B12 in our bodies from plant sources. Strict vegans, and their breast fed infants have been rarely reported to have pernicious anemia because they get no Vitamin B12 from their diets. Most people though, including vegetarians who eat eggs or drink milk, get enough. Why then does anyone develop pernicious anemia?
It turns out that the absorption of Vitamin B12 from our intestine is quite complicated. It requires a protein called intrinsic factor which is secreted by the parietal cells in the stomach, and in most people with pernicious anemia, these cells have been destroyed. It is believed that this destruction is brought about by an autoimmune mechanism, since people with the disease usually have antibodies against intrinsic factor and parietal cells in their blood. The anemia is more common in people who have other autoimmune diseases such as Graves’s disease, thyroiditis, vitiligo and others.
Because the cells produced in this anemia are larger than normal, but fewer in number, a calculation derived from the hematocrit (HCT) and the red cell count (RBC) which is called the mean corpuscular volume (MCV) will always be high, indicating that the cells on average are large.
Pernicious anemia is always treated with Vitamin B12 injections. Because the deficiency stems from failure to absorb B12, taking additional quantities by mouth is not very effective. Folic acid, which is commonly taken as a vitamin supplement can be very harmful for someone with pernicious anemia, because in large doses it can correct the anemia, but will not correct the brain and nerve complications, thus perhaps leading to permanent neurological damage. Once the correct diagnosis has been made, and B12 therapy has begun, one can take folic acid supplements without harm. Cancer of the stomach is more common in people with this anemia, and they do need to be periodically screened for it.
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