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Pernicious anemia (also known as Biermer's anaemia or Addison's anaemia or Addison-Biermer anaemia) is a form of megaloblastic anaemia due to vitamin B12 deficiency dependent on impaired absorption of vitamin B12 in the setting of atrophic gastritis, and more specifically of loss of gastric parietal cells. While the term "pernicious anaemia" is sometimes also incorrectly used to indicate megaloblastic anaemia due to any cause of vitamin B12 deficiency, its proper usage refers to that caused by atrophic gastritis and parietal cell loss only.
Mechanisms & manifestations
Vitamin B12 cannot be produced by the human body, and must therefore be obtained from diet. Normally, dietary vitamin B12 can only be absorbed by the ileum when it is bound by the intrinsic factor produced by parietal cells of the gastric mucosa. In pernicious anaemia, this process is impaired because of loss of parietal cells, resulting in insufficient absorption of the vitamin, which over a prolonged period of time ultimately leads to vitamin B12 deficiency and thus megaloblastic anaemia.
The presentation of pernicious anaemia resembles that of any other form of anaemia, but is often accompanied by the manifestations of vitamin B12 deficiency (notably neurological abnormalities such as peripheral neuropathy), as well as by other manifestations of autoimmune atrophic gastritis.
Most commonly, the cause for impaired binding of vitamin B12 by intrinsic factor is autoimmune atrophic gastritis, in which autoantibodies are directed against parietal cells (resulting in their loss) as well as against the intrinsic factor itself (rendering it unable to bind vitamin B12). Less frequently, loss of parietal cells may simply be part of a widespread atrophic gastritis of non-autoimmune origin, such as that frequently occurring in elderly people affected with long-standing chronic gastritis of any cause (including Helicobacter pylori infection). Note that forms of vitamin B12 deficiency other than pernicious anaemia must be considered in the differential diagnosis of megaloblastic anaemia.
A diagnosis of pernicious anaemia first requires demonstration of megaloblastic anaemia (through a full blood count) and of its direct cause, vitamin B12 deficiency (by measuring B12 levels in serum). A Schillings test can then be used to distinguish pernicious anemia from other causes of vitamin B12 deficiency (notably malabsorption. A diagnosis of atrophic gastritis should be confirmed by gastroscopy with biopsies. Approximately 90% of individuals with pernicious anemia have antibodies for parietal cells; however only 50% of all individuals in the general population with these antibodies have pernicious anaemia.
Being a manifestation of vitamin B12 deficiency, pernicious anaemia is treated by administering vitamin B12 supplements. Note that if oral tablets are chosen for this purposes, much higher doses are given than normally required in order to overcome the impaired absorption that characterises pernicious anaemia. If oral tablets are not desired, vitamin B12 can also be administered via injection, which is usually given once a month. Often the patient can learn to do this at home with the same syringes and needles used for insulin treatment of diabetes.
The treatment for pernicious anemia was first devised by George Whipple who bled dogs to make them anemic and then fed them various substances to see what would make them healthy again, more rapidly. He discovered that ingesting large amounts of liver seemed to cure the disease. George Minot and William Murphy then set about to chemically isolate the curative substance and ultimately were able to isolate the vitamin B12 from liver (ironically, however, it was the iron, not the B-12 in liver which cured the anemia produced by bleeding in dogs). For the discovery of the cure of a previously fatal disease of unknown etiology the three men shared the 1934 Nobel Prize in Medicine. For a time, pernicious anemia was treated by drinking raw liver juice. Eventually as the vitamin was purified and other methods of producing it were developed, pernicious anemia was treated with either vitamin B12 injections, or else large oral doses of vitamin B12, typically between 1 and 4 mg (1000 to 4000 mcg) daily.
Pernicious anemia was once a fatal disease before the year 1926, when doctors gathered together and ran tests on patients. They concluded that continuous B12 injections help the patient's recovery. Previously, Pernicious Anemia victims ate or drank at least 1/2 a pound of raw liver every day for a treatment. Dr. Addison first discovered this disease as a problem and perscribed this, and this is where doctors aqcuire the name Addison's Anemia. Dr. Newcastle found that he could regurgitate his gastric juices and feed it to his patients. This took the place of daily liver, and these people improved. But he could not keep a steady supply, so they continued to eat liver.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pernicious_anemia". A list of authors is available in Wikipedia.|