Leukemia

From the Greek words for white (leukos) and blood (hemia), leukemia refers to abnormally shaped and functioning leukocytes (white blood cells). Because the leukocytes multiply at an uncontrolled and rapid rate, leukemia is considered a cancer of the blood. Leukemia is neither contagious nor infectious, nor acquired from the mother prior to or during birth, but some researchers have suggested genetic predispositions exist for rare forms of leukemia, such as hairy-cell leukemia (HCL) that affects lymphocytes. Emerging evidence links leukemia to the Human T-Cell Lymphotropic Virus (HTLV), the Epstein-Barr Virus (EBV), and even HIV, although causes and risk factors are still poorly understood and fervently contested among scientists. Current research points to the cause of leukemia as a result of an acquired genetic injury to the DNA of a cell, which then multiplies in its damaged form until the disease state is reached.

Leukemia begins in the bone marrow and spreads through the lymph and blood system to tissues, organs, and sometimes testicles, brain, and spinal fluid. Leukocytes normally attack, kill, and help to expel invading microbes, but the leukocytes of patients with leukemia are abnormally shaped, increased in number, and immature of development (termed lymphoblasts). As the lymphoblasts multiply and spread, they outnumber and overwhelm the erythrocytes that transport oxygen and carbon dioxide in opposite directions, and hamper the function of platelets (thrombocytes), which help blood to clot.