Leukemia is a type of cancer found in your blood and bone marrow and is caused by the rapid production of abnormal white blood cells. These abnormal white blood cells are not able to fight infection and impair the ability of the bone marrow to produce red blood cells and platelets.
Leukemia can be either acute or chronic. Chronic leukemia progresses more slowly than acute leukemia, which requires immediate treatment. Leukemia is also classified as lymphocytic or myelogenous (myeloid). Lymphocytic leukemia refers to abnormal cell growth in the marrow cells that become lymphocytes, a type of white blood cell that plays a role in the immune system. In myeloid leukemia, abnormal cell growth occurs in the marrow cells that mature into red blood cells, white blood cells, and platelets. There are four broad classifications of leukemia: acute lymphocytic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL), and chronic myeloid leukemia (CML).
Leukemia occurs in both adults and children. ALL is the most common form of childhood leukemia, and AML is the second most common. Decades of research have led to vastly improved outcomes for children diagnosed with ALL. The two most common adult leukemias are AML and CLL.
Acute lymphocytic leukemia (ALL)
Adult ALL is a type of cancer in which the bone marrow makes too many lymphocytes (a type of white blood cell).
In ALL, too many stem cells become lymphoblasts, B lymphocytes, or T lymphocytes. These cells are also called leukemia cells. These leukemia cells are not able to fight infection very well. Also, as the number of leukemia cells increases in the blood and bone marrow, there is less room for healthy white blood cells, red blood cells, and platelets. This may cause infection, anemia, and easy bleeding. The cancer can also spread to the central nervous system (brain and spinal cord).
Childhood ALL is a type of cancer in which the bone marrow makes too many immature lymphocytes (a type of white blood cell).
In a child with ALL, too many stem cells become lymphoblasts, B lymphocytes, or T lymphocytes. These cells are cancer (leukemia) cells. The leukemia cells do not work like normal lymphocytes and are not able to fight infection very well. Also, as the number of leukemia cells increases in the blood and bone marrow, there is less room for healthy white blood cells, red blood cells, and platelets. This may lead to infection, anemia, and easy bleeding.
Acute myeloid leukemia (AML)
AML is an aggressive (fast-growing) disease in which too many myeloblasts (immature white blood cells that are not lymphoblasts) are found in the bone marrow and blood. Also called acute myeloblastic leukemia, acute myelogenous leukemia, acute nonlymphocytic leukemia, and ANLL.
Chronic lymphocytic leukemia (CLL)
CLL is an indolent (slow-growing) cancer in which too many immature lymphocytes (white blood cells) are found mostly in the blood and bone marrow. Sometimes, in later stages of the disease, cancer cells are found in the lymph nodes and the disease is called small lymphocytic lymphoma.
Chronic myeloid leukemia (CML)
CML is an indolent (slow-growing) cancer in which too many myeloblasts are found in the blood and bone marrow. Myeloblasts are a type of immature blood cell that makes white blood cells called myeloid cells. CML may get worse over time as the number of myeloblasts increases in the blood and bone marrow. This may cause fever, fatigue, easy bleeding, anemia, infection, a swollen spleen, bone pain, or other signs and symptoms. CML is usually marked by a chromosome change called the Philadelphia chromosome, in which a piece of chromosome nine and a piece of chromosome 22 break off and trade places with each other. It usually occurs in older adults and rarely occurs in children. Also called chronic granulocytic leukemia and chronic myelogenous leukemia.
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