Their marked increase (megaloblastosis) is indicative of an "altered synthesis of DNA, classically secondary to a deficiency of vitamin B12 or folic acid. Both of these substances are necessary for the production of red blood cells and their deficiency causes a maturation defect of these elements (in particular, the cytoplasm is excessive compared to the nucleus). Consequently, these elements accumulate in the bone marrow, precisely causing megaloblastosis, while in the peripheral blood, there is a macrocytosis, with red blood cells (or erythrocytes) of size higher than the norm.
The clinical picture of megaloblastic anemia can also be supported by numerous other pathological conditions, congenital or acquired, accumulated by a maturation defect of the erythroid precursors, which prevents the terminal differentiation of erythrocytes.
Megaloblastic anemia is diagnosed through a blood test, aimed in particular at evaluating the mean corpuscular volume of red blood cells (MCV) and other erythrocyte indices.
The therapy of megaloblastic anemia always depends on the cause: if the haematological picture is related to a lack of vitamin B12 or folic acid, it is recommended to take supplements based on these elements and to correct the diet.
responsible for transporting oxygen from the lungs to the tissues. In order to perform their function in the best possible way, these must have the shape of a biconcave disc, with a flattened nucleus and adequate dimensions. When they are larger than normal, erythrocytes are defined as macrocytes (or megalocytes).In detail, based on the size of the erythrocytes it is possible to distinguish:
- Normocytosis: red blood cells are of normal size, ie they have a diameter of 7-8 micrometers (µm).
- Microcytosis: it is characterized by microcytic erythrocytes, that is, smaller than the norm;
- Macrocytosis: it is the opposite condition to microcytosis, in which the erythrocytes have a diameter greater than normal, between 9-12 µm. Megalocytes are red blood cells even larger than macrocytes (diameter greater than 14 µm).
The physical characteristics of red blood cells are defined by the erythrocyte indices. In the context of laboratory analyzes, the most useful haematochemical parameter to determine whether red blood cells are normal, too large or too small, is the mean corpuscular volume (MCV). By definition, macrocytosis (ie the presence of macrocytes in the blood) it exists when the mean cell volume (MCV) is greater than 95 femtoliters (fL); in megaloblastic anemia, this parameter is included or even greater than the range between 100 and 150 fL.
, but numerous conditions, congenital or acquired, united by defects of purine or pyrimidine synthesis, can determine this haematological picture.Megaloblastic anemia is therefore indicative of an ineffective hematopoiesis as regards the cell line of red blood cells and, specifically, is characterized by a delay in DNA synthesis.
This involves a "nucleocytoplasmic maturative asynchrony of the erythroid precursors (from the proerythroblast to the reticulocyte), ie the cells of the bone marrow from which the red blood cells derive have increased size, with an excessive cytoplasm compared to the nucleus.
In the bone marrow, therefore, an ineffective cytogenesis and an early cell death are observed, therefore in megaloblastic anemias the erythroid cells produced in the medulla are largely destroyed, without being able to reach the bloodstream. In the blood count, it is found in association with a macrocytic anemia.
