Concept and etiology
The term is derived from the words leukemia and eides (similar). This definition refers to shifts in the blood system and hematopoietic organs that lead the physician to suspect hemoblastoses. However, such conditions are exclusively reactive in nature and never transform into the pathology they resemble.
The main causes for the development of such conditions include:
- various infections;
- severe intoxications;
- neoplastic processes;
- tumor metastasis to the bone marrow.
Mechanisms of development
The changes in the blood and bone marrow are based on three key pathogenetic mechanisms:
- Enhanced and premature release of immature cellular elements into the bloodstream.
- Significantly increased production of new blood cells.
- Restriction of the physiological exit of mature cells from the blood back into the tissues.
It is worth noting that these processes can affect both the peripheral blood itself and the bone marrow tissue.
Differential diagnosis with hemoblastoses
The key point in clinical practice is distinguishing reactive changes from true blood tumors. Leukemoid reactions are characterized by the following signs:
- Association with the cause: there is always a background primary disease that triggered the shift in laboratory parameters.
- Clinical presentation: the patient's general condition fully reflects the severity of this specific underlying disease.
- Laboratory parameters: the basophil and platelet counts usually remain within the normal range, while the activity of alkaline phosphatase in granulocytes is normal or decreased.
- Cytogenetics: complete absence of the Philadelphia chromosome and other karyotype abnormalities in the bone marrow.
Briefly: answers to topical questions
What types of leukemoid reactions exist according to the myeloid and lymphoid lineages?
Available materials describe only the myeloid-type leukemoid reaction. It represents a hyperregenerative left shift with immature forms. This condition is characterized by the appearance of metamyelocytes, myelocytes, and, more rarely, myeloblasts in the peripheral blood. Such changes resemble the blood picture in myeloid leukemia and are most often combined with pronounced leukocytosis and neutrophilia. The process indicates significant bone marrow irritation and accelerated leukopoiesis against the background of severe infectious, purulent-inflammatory, and septic diseases with preserved body resistance.
The reaction is reversible: treat the cause (infection or intoxicating factor), and leukocytes will return to normal while chromosomes remain intact.
Class and exam questions
Can a leukemoid reaction transform into leukemia?
No, never. These changes are strictly reactive in nature and do not transform into the tumor they resemble.
What is the main quantitative criterion indicating a leukemoid reaction?
The main laboratory criterion is leukocytosis exceeding 40–50×10⁹/L (provided true leukemia is excluded).
What happens to blood parameters after the underlying disease is cured?
Complete reversibility of the process occurs: all blood changes disappear without a trace after the elimination of their underlying cause.
What else to study on this topic
- Detailed analysis of the three development mechanisms at the cellular level
- Specifics of bone marrow changes in reactive conditions
- Assessment of alkaline phosphatase activity in granulocytes
- The role of cytogenetic testing in the diagnosis of hemoblastoses
- Clinical examples of infections and intoxications triggering the reaction
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