Classification of Erythrocytosis
Erythrocytoses are divided into three main groups depending on their mechanisms of development:
- Primary: associated with neoplastic transformation of hematopoietic tissue (e.g., polycythemia vera).
- Secondary: act as a symptom of other disorders, accompanied by the activation of erythropoiesis.
- Relative: occur when plasma volume decreases or erythrocytes are released from storage sites without an increase in their total body mass.
Secondary Absolute Erythrocytosis
Develops as a result of non-neoplastic stimulation of erythropoiesis. The primary regulator is the hormone erythropoietin. Its secretion increases in:
- Chronic hypoxia (respiratory or heart failure, anemias).
- Neoplastic processes in the kidneys or liver.
Unlike polycythemia vera, thrombocytosis and leukocytosis are usually absent here, and elimination of the cause of hypoxia leads to the normalization of blood parameters.
Relative Erythrocytosis
In these conditions, erythrocyte production in the bone marrow is unchanged. Two mechanisms are distinguished:
- Hemoconcentration: fluid loss (vomiting, diarrhea, burns) leading to polycythemic hypovolemia.
- Redistribution: release of stored erythrocytes into the vascular bed during stress or acute hypoxia, causing polycythemic hypervolemia.
Hemodynamic Consequences
High blood viscosity in erythrocytoses inevitably leads to circulatory disorders:
- Arterial hypertension.
- Microcirculatory disturbances (sludge phenomenon, stasis).
- Thrombotic syndrome.
- Paradoxical bleeding due to functional platelet deficiency.