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Leukemoid reaction

Leukemoid reactions are a temporary significant increase in the number of leukocytes in response to any stimulus, accompanied by the appearance in the blood of immature forms of leukocytes. The number of leukocytes in leukemoid reactions can reach 50,000 or more in 1 mm 3 of blood. Unlike leukemia (see), with leukemoid reactions, you can detect the disease that caused it (infections, intoxication, malignant tumors, skull injuries, etc.); in the punctate of the spleen there are no leukemic changes; the blood picture is normalized as the underlying disease is eliminated.

Leukemoid reactions are pathological blood reactions in which the morphological picture of the blood is similar to leukemic or subleukemic patterns, but the pathogenesis of changes is different.

The need to separately consider leukemoid reactions is determined by their qualitative features, which is noted in laboratory blood tests, when the laboratory physician must emphasize the well-known similarity of the blood picture with leukemic. Systematization of the study of leukemoid reactions led to their differentiation from leukemia. Leukemoid reactions are a reflection of the functional state of the hematopoietic apparatus, and their occurrence is determined most often by the individual reactivity of the organism, although there is a group of leukemoid reactions caused by the specificity of the pathogen (infectious low-symptomatic lymphocytosis, infectious mononucleosis).

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The classification of leukemoid reactions should be based primarily on a hematological trait. However, in each case it is necessary to establish the etiology of the leukemoid reaction, which will make it possible to eliminate leukemia and apply a rational treatment of the underlying disease. The following main types of leukemoid reactions are distinguished: 1) myeloid, 2) lymphatic and 3) lympho-monocytic.

Among the leukemoid reactions of the myeloid type, the following subgroups are distinguished. 1. Leukemoid reactions with a blood picture characteristic of chronic myeloid leukemia. Etiology: infections - tuberculosis, dysentery, sepsis, scarlet fever, erysipelas, purulent processes, diphtheria, lobar pneumonia, acute liver dystrophy, acute hemolytic crisis; ionizing radiation - X-rays, radioisotopes, etc .; shock - wound, operating, injuries of a skull; intoxication - by sulfa drugs, bigual, carbon monoxide; taking corticosteroids; lymphogranulomatosis; metastasis of malignant tumors in the bone marrow.
2. Leukemoid reactions of eosinophilic type. Etiology: worm infestation (most often tissue) - opisthorchiasis, fascioliasis, strongyloidosis, trichinosis, etc .; eosinophilic pneumonia (eosinophilic infiltrates in the lungs), allergic leukemoid reactions (administration of antibiotics, medicinal dermatitis, severe universal dermatitis, etc.); the so-called eosinophilic collagenosis (Busse disease); allergic major eosinophilia of unknown origin (duration 1–6 months), ending with recovery; periarteritis nodosa.
3. Leukemoid reaction myeloblastic type. Etiology: sepsis, tuberculosis, metastasis of malignant tumors in the bone marrow.

Among the leukemoid reactions of the lymphatic and lympho-monocytic type, the following subgroups are distinguished.
1. Lympho-monocytic reaction of the blood. Etiology: infectious mononucleosis (specific virus).
2. Lymphatic blood reaction. Etiology: oligosymptomatic infectious lymphocytosis (specific lymphotropic virus).
3. Lymphatic blood reactions in various infections in children (with hyperleukocytosis). Etiology: rubella, whooping cough, chicken pox, scarlet fever, as well as leukemoid lymphocytosis (with hyperleukocytosis) in septic and inflammatory processes, tuberculosis, etc.

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Hematologically, leukemoid reactions of the myeloid type are characterized by the following features: 1) the blood picture is similar to subleukemic in chronic myeloid leukemia; segmented and stab neutrophils dominate in the leukogram and there is never an increase in the percentage of basophils; 2) Unlike leukemia, the toxigenic granularity of neutrophils is more pronounced; 3) in punctates of the spleen (even if it is enlarged) and lymph nodes there are no signs of leukemic myeloid metaplasia; 4) in leukocytes there are no Ph 'chromosomes characteristic of myeloid leukemia; 5) the disappearance of reactions associated with the elimination of the underlying disease.

There are no clinical symptoms of leukemoid reactions; it refers to the underlying disease in which these reactions develop.

It should be noted the appearance of leukemoid reactions on the basis of intoxication with sulfa drugs and bigumalem. Sulfonamide leukemoid reactions are characterized by leukocytosis up to 20 000 with a shift of leukogram to myelocytes and promyelocytes, as well as the development of anemia; duration 2-3 weeks. Bigumal leukemoid reactions usually occur with overdose: the blood picture is subleukemic, there is no anemia, the course is short-lived.

Leukemoid reactions from the action of ionizing radiation occur as a result of the massive action of ionizing radiation and are characterized by subleukemic leukocytosis with a shift to the left to myelocytes, and sometimes also by eosinophilia. These reactions must be differentiated from real leukemias, developing under the influence of ionizing radiation at a later date.

Leukemoid reactions in malignant neoplasms can develop as a result of the action of tumor products (lytic) on the blood-forming organs. Common stomach cancer, metastatic lung cancer (cancer pneumonia, cancer lymphangitis) are sometimes accompanied by leukemoid reactions. However, more often leukemoid reactions occur as a result of irritation with metastases of granulocyte and erythroblastic growths of the bone marrow.

Observed: 1) subleukemic leukemoid pattern with a shift to myelocytes and promyelocytes; 2) myeloblastic leukemoid blood patterns that mimic acute leukemia (disseminated metastases in the bone marrow); 3) most often erythroblast-granulocytic leukemoid reactions.

Recently, eosinophilic leukemoid reactions are especially common. They are observed in a variety of diseases, as well as a combination of certain diseases, usually not accompanied by significant changes in the blood characteristic of leukemoid reactions.

It should be considered that the development of eosinophilic leukemoid reactions depends not only on the specificity of the etiological factor, but also on the uniqueness of the reactivity of the patient.

In recent years, there have been several cases of cyclic febrile illness with a small lymphadenopathy, and sometimes splenomegaly, which were accompanied by leukemoid reactions of the eosinophilic type (IA Kassirsky). The leukocytosis in these cases reaches very large numbers - 50,000–60,000 per 1 mm 3 with a percentage of eosinophils up to 80–90. The disease proceeds more or less hard, but the outcome is favorable in all cases. You can suspect infectious-allergic nature of this form. Busse describes a special form of collagenosis, accompanied by intensive infiltration of almost all organs and tissues of the human body with mature eosinophils, the eosinophilic leukemoid reaction of the blood, often splenosis and hematomegaly, and damage to the heart and lungs. This form is characterized by a progressive course, the prognosis for it is often unfavorable. It is often mistaken for eosinophilic myeloid leukemia.

In tropical countries, there are cases of so-called tropical eosinophilia (not associated with helminthic invasions). Pronounced eosinophilic hyperleukocytosis often occurs when the so-called drug disease. In addition, moderate or large eosinophilia with leukocytosis is considered characteristic of some forms of periarteritis nodosa, asthma (especially in combination with various helminthic invasions), scarlet fever, and rheumatism. Once eosinophilic leukemoid reactions have arisen (even transient ones) are prone to recurrence and often reappear under the influence of a variety of causes after complete normalization of blood.

Leukemoid reactions with myeloblasts in peripheral blood and so-called reactive reticulosis cause the greatest difficulties to determine. It is believed by hematologists that any hemocytoblastemia or myeloblastemia indicates leukemia, which is atypically abrupt due to the addition of an infection (sepsis, tuberculosis), and also in connection with the use of cytotoxic antimetabolites for therapeutic purposes. However, some pathologists tend to treat cases of hemocytoblastemia and reticulosis as leukemoid reactions. In these cases, tuberculosis, sepsis (complicated by reactive reticulosis), and cancer are of primary importance in changes in the blood and blood-forming organs. In favor of this concept they say: histocythomorphological picture of the bone marrow - the presence of normal myeloid tissue, the absence of diffuse proliferation of immature cells; in some cases - poverty by cellular elements, among the surviving cells are many plasma cells, there are foci from hemocytoblasts, in places complete aplasia with foci of regeneration from reticular cells; there is no characteristic leukemic organ metaplasia.

The leukemoid reactions of the lymphatic and monocytic-lymphatic types are characterized by the similarity of peripheral blood with a picture of chronic lymphocytic leukemia or acute leukemia. Such reactions occur as changes in the blood in case of completely independent diseases - viral infectious mononucleosis and low-symptom viral lymphocytosis.

According to the blood picture, leukemoid reactions in low-symptom infectious lymphocytosis and symptomatic leukemoid reactions in whooping cough, chickenpox, rubella, scarlet fever are identical. Leukocytosis usually reaches 30,000–40,000 and even 90,000–140,000. In the leukogram, lymphocytes usually predominate, but a known percentage of macrogeneration of lymphocytes, atypical lymphocytes, and reticular cells can be detected. When oligosymptomatic infectious lymphocytosis there is an increased percentage of eosinophils and polysegmental neutrophils.

With a differential diagnosis from a blood picture in chronic lymphocytic leukemia, one should take into account the presence of a large percentage of leukolysis cells in lymphocytic leukemia and a small percentage of them in leukemoid lymphocytosis; In addition, lymphatic leukemoid reactions such as infectious lymphocytosis occur in children from 2–3 to 14–15 years old, and chronic lymphocytic leukemia occurs in people over 40 years old. It is necessary to emphasize the rapid disappearance of leukemoid lymphocytosis - the number of leukocytes and the blood count return to normal after 5 to 7 weeks.