Leukemoid Reactions

Changes in the blood and hematopoietic organs, reminiscent of leukemia and other tumors of the hematopoietic system, but always having a reactive nature and not transforming into the tumor they resemble. Can be caused by various infections, intoxications, tumors, metastases of tumors to the bone marrow.

Pathogenesis. The mechanism of development is different for different types of reactions: in some cases there is the release of immature cellular elements into the blood, in others there is an increased production of blood cells or a restriction of the release of cells into the tissue, or the presence of several mechanisms at the same time. Leukemoid reactions may involve changes in the blood, bone marrow, lymph nodes, and spleen. A special group of reactions consists of changes in protein fractions of the blood, simulating tumors of the immunocompetent system - myeloma, Waldenström's macroglobulinemia.

Leukemoid reactions of the granulocytic type, reminiscent of chronic myeloid leukemia or subleukemic myelosis, accompany severe infections and intoxications. In the blood, neutrophilic leukocytosis is noted with a shift in the nuclear formula to myelocytes. Unlike chronic myeloid leukemia, reactive leukocytosis is always based on a severe process, accompanied by an increase in body temperature, the presence of inflammatory foci, and sepsis.

It is with the massive death of microbial bodies and the entry of endotoxin into the blood that the release of the bone marrow granulocyte reserve into the blood and the increased production of granulocytes are associated. At the beginning of chronic myeloid leukemia and with subleukemic myelosis, with which the inflammatory picture of the blood can be confused, no intoxication is observed, the patient is completely somatically preserved.

In doubtful cases, dynamic observation will eliminate diagnostic difficulties: either the inflammatory process will become obvious, or a steady increase in the number of leukocytes will serve as the basis for a special study of the bone marrow.

Occasionally, neutrophilic leukocytosis without significant rejuvenation of the formula is observed in cancer, but in chronic myeloid leukemia there is always a “rejuvenation” of the formula to myelocytes and iromyelocytes.

Eosinophilic blood reactions accompany allergic diathesis, sensitization of the body by parasites, drugs, and occasionally tumor growth. High blood eosinophilia requires careful examination: first of all, the exclusion of drug sensitization and parasite infestation. In rare cases, high eosinophilia may reflect a reaction to acute aleukemic T-cell leukemia. Therefore, with unmotivated high eosinophilia, a comprehensive examination is necessary to exclude cancer, including bone marrow puncture.

Reactive erythrocytosis quite often serves as a subject for differential diagnosis with erythremia. The cause of erythrocytosis is most often lung diseases with decreased blood oxygenation, congenital heart defects, and arteriovenous aneurysms. High erythrocytosis, sometimes with a slightly increased platelet count, is observed in hypernephroid kidney cancer.

Myelemia is the presence in the blood of bone marrow cells - myelocytes, promyelocytes, erythrokaryocytes, and less commonly megakaryocyte nuclei. This picture may to some extent resemble acute erythromyelosis, from which it is distinguished by the absence of blast cells, which are present in large numbers in the blood during this leukemia. Myelemia occurs with miliary metastases of cancer to the bones.

Leukemoid reactions of the lymphatic type are most often caused by a viral infection. The most common reactive lymphocytosis is low-symptomatic infectious lymphocytosis. Based on the blood picture, it can easily be mistaken for chronic lymphocytic leukemia, but it occurs almost exclusively in children, and they do not have chronic lymphocytic leukemia. Reactive lymphocytosis may occur after splenectomy.

Leukemoid