The terms acute and chronic refer to the duration of the untreated disease. Before the advent of mod.... cell leukemia

Leukemia primarily involves the bone marrow, but the lymph nodes and spleen may also be affected. For example, the spleen usually is enlarged in chronic myelogenous leukemia, and in chronic lymphocytic leukemia there often is enlargement of lymph nodes. Acute leukemia is marked by the presence in the blood of immature cells normally not found there. In acute lymphocytic anemia (also called acute lymphoblastic leukemia), most frequently seen in children, the cells are immature forms of the lymphatic series of cells. In a third and the least common variety, acute monocytic leukemia, the immature cells appear to be precursors of the monocytes of the blood. In all forms of acute leukemia the typical cells are found in abundance in the bone marrow. Aleukemic leukemia refers to those instances of leukemia in which no abnormal cells are found in the blood; in these instances the leukemia is identified by examinations of the bone marrow. Chronic granulocytic (myelogenous) leukemia i! s characterized by the appearance in the blood of large numbers of immature white cells of the granulocytic series in the stage following the myeloblast, namely, myelocytes. The disease then often terminates in a form resembling acute leukemia (blastic crisis). Treatment of all types of leukemia reduces illness and, in acute leukemia, prolongs life. The therapeutic agents are all myelotoxic; i.e., they injure all the cells of the bone marrow, normal cells as well as leukemic cells. Their mode of action is through direct damage to the dividing stem cell (unspecialized cell from which specialized cells develop) or by slowing or cessation of cell division. These effects may be accomplished (1) by , substances that interfere with the synthesis of DNA, a constituent of the chromosomes in the cell nucleus; (2) by blocking DNA strand duplication through the binding of drugs such as the nitrogen mustards with the base groups of DNA; (3) by disruption of the mitotic spindle during c! ell division; or (4) by interfering with the formation or func! tioning of RNA, which is manufactured in the cell nucleus and plays an essential role in the production of protein and in other cell functions. Acute lymphoblastic leukemia is more successfully treated than are other forms of acute leukemia; prolonged remissions and even cures can be brought about in children with the disease. Acute myeloblastic leukemia and acute monocytic leukemia are less effectively treated by available drugs than is acute lymphoblastic leukemia. Transplantation of normal bone marrow, following total irradiation of the patient to destroy all his normal bone marrow cells as well as the leukemic cells, has shown promise. Although the treatment is arduous and complex, cures of acute lymphocytic and acute myelogenous forms of leukemia are now possible with bone marrow transplantation. In its early stages, chronic lymphocytic leukemia seems best untreated, as long as anemia is not present or glandular enlargement is not too troublesome. Another malignant dis! ease, probably related to the above conditions, is , which is characterized by a malignant overgrowth of plasma cells within the bone marrow. As the bone marrow becomes more involved, anemia develops and hemorrhages occur: the number of leukocytes may be low, and abnormal myeloma or plasma cells are found in the bone marrow. cell leukemia