Leukemia is a term for cancers of the blood cells. Leukemia starts in blood-forming tissues such as the bone marrow. Your bone marrow makes the cells which will develop into white blood cells, red blood cells, and platelets. Each type of cell has a different job:

• White blood cells help your body fight infection
• Red blood cells deliver oxygen from your lungs to your tissues and organs
• Platelets help form clots to stop bleeding

When you have leukemia, your bone marrow makes large numbers of abnormal cells. This problem most often happens with white blood cells. These abnormal cells build up in your bone marrow and blood. They crowd out the healthy blood cells and make it hard for your cells and blood to do their work.

There are different types of leukemia. Which type of leukemia you have depends on the type of blood cell that becomes cancer and whether it grows quickly or slowly.

The type of blood cell could be:

• Lymphocytes, a type of white blood cell
• Myeloid cells, immature cells that become white blood cells, red blood cells, or platelets

The different types can grow quickly or slowly:

• Acute leukemia is fast growing. It usually gets worse quickly if it's not treated.
• Chronic leukemia is slow growing. It usually gets worse over a longer period of time.

The main types of leukemia are:

• Acute lymphocytic leukemia (ALL), which is the most common type of cancer in children. It can also affect adults.
• Acute myeloid leukemia (AML), which is more common in older adults but can also affect children
• Chronic lymphocytic leukemia (CLL), which is one of the most common types of leukemia in adults. It often occurs during or after middle age.
• Chronic myeloid leukemia (CML), which usually occurs in adults during or after middle age

Leukemia happens when there are changes in the genetic material (DNA) in bone marrow cells. The cause of these genetic changes is unknown.

For the specific types, there are different factors which can raise your risk of getting that type. Overall, your risk of leukemia goes up as you age. It is most common over age 60.

Some of the symptoms of leukemia may include:

• Feeling tired
• Fever or night sweats
• Easy bruising or bleeding
• Weight loss or loss of appetite
• Petechiae, which are tiny red dots under the skin. They are caused by bleeding.

Other leukemia symptoms can be different from type to type. Chromic leukemia may not cause symptoms at first.

Your health care provider may use many tools to diagnose leukemia:

• A physical exam
• A medical history
• Blood tests, such as a complete blood count (CBC)
• Bone marrow tests. There are two main types - bone marrow aspiration and bone marrow biopsy. Both tests involve removing a sample of bone marrow and bone. The samples are sent to a lab for testing.
• Genetic tests to look for gene and chromosome changes

Once the provider makes a diagnosis, there may be additional tests to see whether the cancer has spread. These include imaging tests and a lumbar puncture, which is a procedure to collect and test cerebrospinal fluid (CSF).

The treatments for leukemia depend on which type you have, how severe the leukemia is, your age, your overall health, and other factors. Some possible treatments might include:

• Chemotherapy
• Radiation therapy
• Chemotherapy with stem cell transplant
• Targeted therapy, which uses drugs or other substances that attack specific cancer cells with less harm to normal cells

NIH: National Cancer Institute