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Endocrinology

Insufficiency of B12 vitamin

Insufficiency of B12 vitamin (cyanocobalamine) is shown by defeat of the hemopoietic fabric, digestive and nervous systems. At avitaminosis B12-scarce anemia (pernicious anemia) and a funicular myelosis develop. The last syndrome seldom arises independently, usually it is combined with megaloblastny anemia. Gipovitaminoza can be followed by slight paresthesias in extremities, burning in language, moderate macrocytic (hyperchromic) anemia.

Epidemiology
Insufficiency of cyanocobalamine meets in the different countries and regions. It comes to light with an identical frequency among men and women. B12-scarce anemia usually develops at persons of middle and advanced age. Increase of this illness at the people who are not using some meat and dairy products is noted. Among groups there are population in which the invasion a wide tape-worm quite often is registered (Karelia, some Areas of Siberia, etc.), find cases of botriotsefalny B12-scarce anemia.

Pathogeny
Cyanocobalamine belongs to water-soluble vitamins. In the greatest number it contains in a liver of fishes and a cattle, kidneys; it is much less than it in meat, eggs, milk, soy. It is soaked up generally in an ileal gut, synthesized also by intestinal microflora. Daily requirement of 3 mg (at pregnant 4 mg). Participates in transfer of methyl groups, in synthesis of nucleic acids, in an exchange of tetrahydrofolic acid. Insufficiency of B12 vitamin seldom happens exogenous, is incomparable more often — endogenous. This group of mechanisms includes the increased B12 vitamin consumption (helminthoses, especially a diphyllobotriasis; pregnancy) and disturbance of its absorption of the different nature. The last can be caused by lack of the stomach of the gastromucoprotein necessary for cyanocobalamine absorption developed by fundal glands (B12-scarce anemia, sometimes cancer or stomach polyposes, a gastrectomy, a subtotal resection of a stomach) or a sprue (a spra, heavy enterita, entero-enteroanastomoses, a resection of considerable part of a small bowel, etc.).

The expressed endogenous deficit of cyanocobalamine causes disturbance of an exchange of nucleic acids in blast cells of an erythroidal row that leads to development of megaloblastny anemia. In lateral and back cords of a spinal cord the degenerative and focal necrotic changes which are coming to the end with a sklerozirovaniye therefore the syndrome of a fuiikulyarny myelosis forms develop.

Classification
There is no standard classification of B12 vitamin deficiency. Almost usually use the classification based on the pathogenetic and clinical principles. Respectively distinguish exogenous (alimentary) and endogenous (from disturbance of absorption or the increased consumption) types of insufficiency of cyanocobalamine. From the last group allocate as an independent nosological form megaloblastny anemia, and sometimes and a funicular myelosis. Other kinds of endogenous insufficiency of B12 vitamin developing as a result of a various serious illness of a stomach and intestines or big operations on these bodies are symptomatic.

Approximate formulation of the diagnosis:
1. B12-scarce anemia (Addison's anemia — Birmera), a medium-weight current, in an aggravation phase.
2. Insufficiency of B12 vitamin of moderate degree, exogenous (alimentary), unsharp hyperchromic anemia, neuralgia.
3. Diphyllobotriasis, secondary B12-scarce anemia of heavy degree.
4. A state after a subtotal resection of a stomach concerning its extended a polypose, symptomatic B12-scarce anemia.
5. To Spr, enterogenous exhaustion, symptomatic B12-foliyevodefitsitnaya anemia.

Preliminary diagnosis
Diagnosis of B12-scarce of anemia is based on identification of three main syndromes: megaloblastny (hyperchromic) anemia, a histamine - a steady achlorhydria of a stomach, a funicular myelosis, and polyneuropathy. Also the glossitis is characteristic. Quite often, however, at avitaminosis of B12 of the expressed phenomena of a funicular myelosis do not find and neurologic frustration are limited only to unsharp polyneuropathy of the lower extremities that is connected, apparently, with progress of replacement therapy.

Diagnosis of a hypovitaminosis of B12 on the basis of only clinical criteria is very complicated. Can be its nonspecific signs: deterioration in appetite, an unstable chair, pallor of skin and mucous membranes, feeling of easy burning in language, reddening of its tip, unsharp paresthesias of legs. Diagnostic value of these signs amplifies if there are relevant anamnestic data (alimentary disturbances) or the disease is found.

More detailed diagnosis and treatment of B12-scarce anemia at which cyanocobalamine absorption processes can worsen. Laboratory identification even unsharp macrocytic (normo-, hyperchromic) anemias significantly supports diagnosis.

Verification of the diagnosis
Diagnosis of the developed stage of avitaminosis of B12 of special difficulties does not cause. The clinical picture has a certain similarity to an infectious endocarditis and some forms of the acquired hemolitic anemias. However at these diseases signs of a funicular myelosis are not observed, and anemia happens hypo - or normokhromny. Besides each of diseases has the specific characters (for example, heart disease at an infectious endocarditis). In doubtful cases for the purpose of differential diagnosis carry out a sternal puncture (or a trepanobiopsiya of a wing of an ileal bone). Detection in marrow of megaloblasts and megaloytes finally verifies the diagnosis.

Diagnostic doubts can arise when avitaminosis of B12 develops at elderly people with an idiopathic hypertensia and obliterating atherosclerosis of arteries of the lower extremities. In these cases of dizziness, caused by anemia, can mistakenly be estimated as hypertensive crises, and paresthesias in legs as displays of ischemia. The doctor has to remember the possibility of the considered combined pathology and not pass symptoms of anemia, a glossitis, changes of tendon jerks. Clinical blood test is obligatory that it can solve the diagnosis.

After at the patient insufficiency of B12 vitamin is clinically established, it is necessary to carry out differential diagnosis between exogenous (alimentary) insufficiency, B12-scarce anemia, endogenous symptomatic insufficiency of B12 caused by tumoral damage of a stomach (cancer or polyposes), and botriotsefalny anemia. The exogenous option of avitaminosis B12 which is very seldom found under our conditions can be diagnosed at reliable establishment of long insufficient intake of cyanocobalamine with food and at an exception of endogenous disturbances of absorption of vitamin. At botriotsefalny anemia signs of damage of a spinal cord are practically not observed; symptoms of helminthoses are characteristic (unpleasant feelings in a stomach, nausea, a skin itch, the expressed eosinophilia, an otkhozhdeniye of joints of worms, eggs of worms in Calais). For identification or an exception of a tumor of a stomach conduct X-ray inspection it and gastroscopy. In all doubtful cases the sternal puncture is carried out. At patients after traumatic stomach and intestines operations (a gastrectomy, a subtotal resection of a stomach, an enterectomy, entero-enteroanastomoses, etc.) at a serious illness of a small bowel (a spra, a terminal ileitis) it is necessary to reveal attentively clinical symptoms of insufficiency of B12 vitamin, since nonspecific precursory symptoms (see above).

Auxiliary value in these cases has determination of concentration of B12 vitamin and its metabolites in blood and urine. At deficit of cyanocobalamine its content in daily urine lower than 20 ng, and methyl-malonic acid — is higher than 5 mg, In blood serum concentration of B12 vitamin is lower than 100 ng/ml. These laboratory researches are conducted also at suspicion on exogenous (alimentary) development of deficit of B12 vitamin and in all not clear cases.

Treatment and prevention
Use B12 vitamin drugs. Depending on weight enter 100 — 500 mkg daily into a muscle within 7 — 10 days, then intervals between injections gradually increase: 3 — 5 — 7 days.

Prevention at almost healthy people is provided with the balanced diet including meat and fish products. Regular inclusion in a diet of milk and soy is useful for vegetarians. After laboratory researches (see above) it is possible to recommend parenteral administration of 50 — 100 mkg of drug of B12 1 — 2 vitamin of time a month or daily reception of the tablets containing cyanocobalamine.

For the purpose of prevention it is important to reveal also timely patients with a diphyllobotriasis (carriers of a wide tape-worm); to make deworming. At the diseases (and after operations) which are followed by cyanocobalamine absorption disturbance follows under control of laboratory researches (content of B12 vitamin in urine and blood) to appoint medical or preventive courses of vitamin therapy.

 
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