By the term megaloblastic anemia (synonyms: Alimentary folic acid deficiency anemia; Alimentary vitamin B12 deficiency anemia; Anaemia perniciosa; Anaemia perniciosa progressiva idiopathica; Anemia, megaloblastic; Congenital pernicious anemia; Congenital intrinsic factor deficiency; B12 deficiency anemia; Folic acid anemia; Folic acid deficiency anemia; Megaloblastic alimentary anemia; Megaloblastic anemia; Megaloblastic anemia; Megalocytic anemia; Pernicious anemia; Vitamin B12 deficiency anemia; Vitamin B12 deficiency anemia in vegetarian; Vitamin B12 deficiency anemia due to intrinsic factor deficiency; ICD-10-GM D53. 1: Other megaloblastic anemias, not elsewhere classified; ICD-10-GM D51.-: Vitamin B 12 deficiency anemia; ICD-10-GM D52.-: Folic acid deficiency anemia) refers to anemia (anemia) caused by a deficiency of vitamin B12 or, less commonly, by a deficiency of folic acid. In exceptional cases, it may also be due to various other causes.
Megaloblastic anemia belongs to the hyperregenerative anemias, i.e. it is characterized by compensatory increased erythropoiesis (formation of mature erythrocytes from hematopoietic stem cells of the hematopoietic bone marrow) with peripheral reticulocytosis.
Deficiency of vitamin B12 leads to a disturbance of DNA synthesis, i.e. cell division is disturbed, but cell growth is not impaired. Consequently, the number of erythrocytes (red blood cells) is reduced. However, they contain more hemoglobin (MCH ↑; mean hemoglobin content per erythrocyte/mean blood pigment content per red blood cell), which is called hyperchromic, and they are much larger (MCV ↑; mean red cell individual volume), which is called macrocytic. This explains why megaloblastic anemia is also called macrocytic hyperchromic anemia.
Pernicious anemia (synonym: Biermer’s disease) is the most common subtype of vitamin B12 deficiency anemia. In this form, intrinsic factor (IF) produced by gastric parietal cells is not produced due to gastric mucosal changes (chronic gastritis type A). Intrinsic factor complexes with dietary vitamin B12 (cobalamin), allowing absorption (uptake) of the vitamin in the terminal ileum (last part of the small intestine). Another form of megaloblastic anemia is folic acid deficiency anemia.
The normal folic acid level in the blood is 3-15 ng/ml. Normal vitamin B12 blood level at 200-900 pg/ml. At least 2.5 µg of vitamin B12 and 400 µg of folic acid should be consumed daily.
Peak incidence: the disease occurs predominantly in older age.
The incidence (frequency of new cases) is approximately 9 cases per 100,000 inhabitants per year (in Germany).
Course and prognosis: The treatment of the underlying disease is in the foreground. The vitamin B12 deficiency can lead to neurological symptoms such as numbness in the extremities or muscle weakness. In the early stages, these sequelae are reversible. In addition to causal therapy, symptomatic treatment, i.e., vitamin B12 substitution, is given.
