The Leukemias

Uncontrolled production of white blood cells can be

caused by cancerous mutation of a myelogenous or

lymphogenous cell. This causes leukemia, which is

usually characterized by greatly increased numbers

of abnormal white blood cells in the circulating

blood.

Types of Leukemia. Leukemias are divided into two

general types: lymphocytic leukemias and myelogenous

leukemias.The lymphocytic leukemias are caused

by cancerous production of lymphoid cells, usually

beginning in a lymph node or other lymphocytic tissue

and spreading to other areas of the body. The second

type of leukemia, myelogenous leukemia, begins by

cancerous production of young myelogenous cells in

the bone marrow and then spreads throughout the

body so that white blood cells are produced in many

extramedullary tissues—especially in the lymph nodes,

spleen, and liver.

In myelogenous leukemia, the cancerous process

occasionally produces partially differentiated cells,

resulting in what might be called neutrophilic

leukemia, eosinophilic leukemia, basophilic leukemia,

or monocytic leukemia. More frequently, however, the

leukemia cells are bizarre and undifferentiated and

not identical to any of the normal white blood cells.

Usually, the more undifferentiated the cell, the more

acute is the leukemia, often leading to death within a

few months if untreated.With some of the more differentiated

cells, the process can be chronic, sometimes

developing slowly over 10 to 20 years. Leukemic

cells, especially the very undifferentiated cells, are

usually nonfunctional for providing the normal protection

against infection.

Effects of Leukemia on the Body

The first effect of leukemia is metastatic growth of

leukemic cells in abnormal areas of the body.

Leukemic cells from the bone marrow may reproduce

so greatly that they invade the surrounding bone,

causing pain and, eventually, a tendency for bones to

fracture easily.

Almost all leukemias eventually spread to the

spleen, lymph nodes, liver, and other vascular regions,

regardless of whether the origin of the leukemia is in

the bone marrow or the lymph nodes. Common effects

in leukemia are the development of infection, severe

anemia, and a bleeding tendency caused by thrombocytopenia

(lack of platelets). These effects result

mainly from displacement of the normal bone marrow

and lymphoid cells by the nonfunctional leukemic

cells.

Finally, perhaps the most important effect of

leukemia on the body is excessive use of metabolic

substrates by the growing cancerous cells. The

leukemic tissues reproduce new cells so rapidly that

tremendous demands are made on the body reserves

for foodstuffs, specific amino acids, and vitamins. Consequently,

the energy of the patient is greatly depleted,

and excessive utilization of amino acids by the

leukemic cells causes especially rapid deterioration of

the normal protein tissues of the body.Thus, while the

leukemic tissues grow, other tissues become debilitated.

After metabolic starvation has continued long

enough, this alone is sufficient to cause death.