Leukemia is a type of cancer that affects the tissues that form blood, the lymphatic system, and the bone marrow. The white blood cells (WBC) help fight infections. Healthy white blood cells are necessary for us to remain healthy. But when a person is affected by leukemia, the WBCs produced by the bone marrow are not normal and do not function properly. Leukemia types can be classified on two parameters: the first being based on the type of WBC they affect, and second on the frequency by which they progress.

1. Types of leukemia
There are many types of leukemia that exist. Some are common and a few are rare. Some leukemia types are very common in children while some forms occur mostly in adults.

2. Common types of leukemia
The most common leukemia types are:

• Chronic Lymphocytic Leukemia (CLL)

CLL is a very common type of leukemia that occurs among older adults. It begins in the B lymphocytes. With the growth of abnormal cells, the normal healthy cells get eradicated.

• Acute Myeloid Leukemia (AML)

Very common in adults, AML affects any component of the blood. There are many subtypes of this form of leukemia. In AML, the myeloid stem cells mature into abnormal myeloblasts normally. At times, they mature into platelets or abnormal blood cells. Once they start multiplying, they destroy the normal cells present in the blood and bone marrow. They can also spread to other parts of the affected person.

• Acute Lymphocytic Leukemia (ALL)

This type of leukemia can affect the bone marrow all over the body. It can spread to other parts such as the liver, lymph nodes, etc. In ALL, leukemia begins in the T or B lymphocytes.

3. Rare types of leukemia

The rare leukemia types include:

• Chronic Myeloid Leukemia (CML)

A rare occurrence, CML affects more adults than children. It occurs when a genetic change in the normal myeloid cells gets converted into immature cancer cells. The abnormal cells then multiply to out-measure the healthy cells in the blood and bone marrow.

• Hairy Cell Leukemia (HCL)

Named after how it looks under a microscope, hairy cell leukemia is one of the rare leukemia types that affect a few thousand individuals every year. The symptoms do not appear immediately. Rather, it takes years before the symptoms start to show up for HCL. It also grows slowly. HCL is a subtype of the CLL type of leukemia. It occurs when the bone marrow makes a lot of B cells. With the increase in these cells, there is a decrease in the production of WBCs, RBCs, and platelets.

Leukemia types are also classified depending on how fast it develops, namely acute and chronic. In the former type, the cells are fast-growing while in the latter, the cells grow slowly. A diagnosis of any type is not easy to handle. All questions should be properly addressed after consulting a doctor.