Leukemia

Leukemia is a cancer of blood cells that starts in your bone marrow, the spongy part inside your bones that makes blood cells. When you have leukemia, your bone marrow makes too many abnormal cells, usually white blood cells, which crowd out healthy cells and prevent your blood from working properly.

In leukemia, your bone marrow produces large numbers of abnormal cells that build up in your blood and bone marrow. These abnormal cells crowd out healthy white blood cells, red blood cells, and platelets, making it hard for your body to fight infections, carry oxygen, and stop bleeding.

Abnormal white blood cells multiply much faster than normal cells and don't die when they should, so they keep building up and taking up space. This crowding prevents healthy blood cells from doing their jobs of fighting infection, carrying oxygen, and forming clots.

Acute leukemia grows quickly and gets worse fast, while chronic leukemia grows slowly over time. The type you have depends on which blood cell becomes cancerous and how fast it multiplies.

The two main types based on cell type are lymphocytic leukemia (affecting lymphocytes, a type of white blood cell) and myeloid leukemia (affecting immature cells that become white blood cells, red blood cells, or platelets).