B12 deficiency anemia: signs, causes, diagnosis, and treatment

B12 deficiency anemia is a form of megaloblastic anemia that occurs due to a deficiency of vitamin B12 (cyanocobalamin) in the body. Vitamin B12 It is necessary for the normal formation of red blood cells, DNA synthesis, and functioning of the nervous system. Its deficiency can lead to serious changes in both the hematopoietic and nervous systems.

Causes of vitamin B12 deficiency

• Insufficient dietary intake. This is common among vegans, because B12 is only found in animal products: meat, eggs, dairy products, and fish.

• Malabsorption in the gastrointestinal tract. Atrophic gastritis, resection of the stomach or small intestine, Crohn's disease, celiac disease can interfere with the absorption of the vitamin.

• Castle's intrinsic factor deficiency. Without this substance, which is produced by the stomach lining, B12 cannot enter the blood. This is seen in pernicious anemia (an autoimmune disease of the stomach).

• Long-term medication use. For example, proton pump inhibitors or metformin can reduce the absorption of vitamin B12.

Symptoms of B12 deficiency anemia

Symptoms develop gradually and are often disguised as other diseases:

• Chronic fatigue, weakness

• Pale skin, shortness of breath during physical exertion

• Tingling, numbness of the extremities

• Gait disturbance, unsteadiness

• Irritability, depressed mood

• Glossitis (painful, «lacquered» tongue)

• Memory impairment, concentration

Diagnostic methods

To make a diagnosis, it is important to conduct a comprehensive laboratory examination:

1. Complete blood count
Macrocytic anemia is detected: enlarged erythrocytes (MCV > 100 fl), decreased hemoglobin level, hyperchromia, neutrophils with segmented nuclei.

2. Biochemical analysis
Serum vitamin B12 levels are assessed. The normal range is 200–900 pg/mL. Values below 200 are diagnostically significant. Additionally, levels of folic acid, homocysteine, and methylmalonic acid are measured.

3. Antibodies to intrinsic factor
Helps establish the autoimmune nature of the deficiency.

4. Morphological study
Bone marrow aspirate shows megaloblastosis, characteristic of B12-deficiency anemia.

5. Other examinations
Gastroscopy to rule out gastritis, Helicobacter pylori infection, and pernicious anemia.

Treatment of B12 deficiency anemia

• Replacement therapy
  In most cases, parenteral administration of cyanocobalamin (in/m or p/s) is used. The classic regimen: 500–1000 mcg daily for 1–2 weeks, followed by a maintenance dose.

• A diet rich in B12
  Beef, liver, seafood, eggs, cheese, and milk are key sources of the vitamin.

• Treating the underlying cause
  For example, eradication of H. pylori, correction of autoimmune gastritis, change of pharmacotherapy.

• Performance monitoring
  After 1–2 weeks, check reticulocytes; after 1–2 months, check hemoglobin and vitamin B12 levels.

Since symptoms of B12 deficiency can be nonspecific, early diagnosis is the key to effective treatment. Patients at risk are advised to have their vitamin B12 levels checked annually, especially if they follow restricted diets, have chronic gastropathy, or have neurological disorders.