Leukemia is a type of cancer that occurs due to the rapid overproduction of abnormal white blood cells. It is the most common form of blood cancer that mostly affects people over the age of 55. It is also the most common type of cancer that affects children under the age of 15.

White blood cells (WBCs) help the body fight infections. These cells grow and divide in a systematic way, as and when your body needs them. In the case of people with leukemia, the bone marrow begins to produce mutated WBCs at an abnormally high rate. Over time, these cells crowd out the healthy blood cells in the bone marrow, leading to a reduced number of healthy white blood cells, red blood cells, and platelets. Due to this, a person may start experiencing the symptoms of leukemia.

Classification of Leukemia
Leukemia is classified on the basis of two factors:

• Its rate of progression
• Type of cells involved

On the basis of its rate of progression, leukemia is of two types:

• Acute leukemia: In this condition, the abnormal white blood cells are immature, which means they are unable to carry out their normal functions. On the other hand, they multiply rapidly because of which the condition worsens quickly. Acute leukemia requires immediate and aggressive medical attention.
• Chronic leukemia: This condition involves more mature cells. Chronic leukemia is further subdivided into various types. In some cases, too many cells are produced, whereas, in others, these cells are under-produced. As compared to acute leukemia, in this condition, the cells multiply slowly and function normally for a long time. Because of this slow cell multiplication rate, cases of chronic leukemia do not have any early symptoms. In many people, the condition goes undiagnosed for several years.

Leukemia can also be classified on the basis of the type of cells involved:

• Lymphocytic leukemia: This type of leukemia attacks the lymphocytes, which form the lymphatic tissue. The lymphatic tissues make up the body’s immune system.
• Myelogenous leukemia: This type of cancer affects the myeloid cells, which assist in the production of red blood cells, white blood cells, and platelets cells.

Types of Leukemia

• Acute lymphocytic leukemia (ALL): This is the most common type of cancer that affects children. It may also occur in adults.
• Chronic lymphocytic leukemia (CLL): This is the most common form of chronic leukemia that affects adults and may go unnoticed for several years.
• Acute myelogenous leukemia (AML): This is the most common type of acute leukemia that is found in adults, but it can affect children as well.
• Chronic myelogenous leukemia (CML): This is mainly seen in adults, and children rarely develop this form of leukemia. The condition may not cause any symptoms for a few months or years before the cancer cells begin to multiply at an abnormally high pace.

Other than these, there are some other rare types of leukemia like myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), and hairy cell leukemia.