Leukemia is one of the most complex types of cancer, and there are many types and subtypes. Not all of them are common, but if we want to study leukemia, we should understand a bit or each and their differences.
Leukemia can be divided into the following types:
Acute lymphoblastic leukemia (ALL)
It is a rapidly progressing type of leukemia where healthy cells are replaced by immature cells that divide rapidly and replace fully functional white blood cells. Immature cells in acute lymphoblastic leukemia are lymphocytes, and they typically invade tissues and organs, including the lymph nodes and the liver.
In this type of leukemia, patients have more B cells than T cells, and even though the onset can occur at any age, it is more common under the age of 15 years old and in older adults. If you want to read more about this type of leukemia, we have written a special article for that purpose.
Acute myeloid leukemia (AML)
It is a fast-growing type of leukemia featuring white blood cells undergoing exaggerated division when they are still immature. In acute myeloid leukemia, the bone marrow creates cells called blasts, and release them prematurely into the bloodstream. The aberrant cells crowd out space in the blood, and other cell lines become affected, including red blood cells and platelets.
Symptoms typically include fever and frequent infections, anemia, and easy bruising and bleeding. Some patients may also develop bone pain and joint pain. There is more information about acute myeloid leukemia in our article devoted to this disease.
Acute Promyelocytic Leukemia
It is a subtype of acute myeloid leukemia that deserves special consideration because it is the most aggressive and life-threatening. In this type of leukemia, there are excessive promyelocytes in the bone marrow. These cells are precursors of white blood cells, and they take up extra space in the bone marrow, not allowing for the appropriate formation of other cell lines, including red blood cells and platelets.
Acute promyelocytic leukemia is more common in older adults and middle-aged adults, but people of all ages can have this type of leukemia. The diagnosis is made by performing a series of tests and detecting a few proteins and chromosomal aberrations in bone marrow samples.
Chronic lymphocytic leukemia (CLL)
It is a slow-progressing blood cancer featuring an exaggerated replication of lymphocytes in the bone marrow. In time, excess lymphocytes spread into the blood and infiltrate organs and lymph nodes. This disease typically takes several years to develop, and patients may be asymptomatic when the disease is detected.
In a later phase of the disease, different blood cell lines in the bone marrow become affected. Thus, patients start displaying low levels of red blood cells (anemia), a reduction of blood platelets (thrombocytopenia), and reduction in functioning lymphocytes (leukopenia). If you want to know more, we have an article entirely devoted to chronic lymphocytic leukemia.
Chronic myeloid leukemia (CML)
It is also known as chronic myelogenous leukemia, and it is a slow-progressing disease affecting the bone marrow. Chronic myeloid leukemia features an abnormal chromosome called the Philadelphia chromosome, which is important to make the diagnosis.
Similar to other types of leukemia, this type spreads to other organs, and the aberrant cells infiltrate almost every organ of the body.
Treatment options for chronic myeloid leukemia typically include immunotherapy, radiation therapy, or chemotherapy. However, some patients may require a stem cell transplant to cure the disease, depending on their age and health parameters.
There’s more information about chronic myeloid leukemia in a particular article we have written for that purpose.
Chronic myelomonocytic leukemia
It is a relatively uncommon type of leukemia with shared characteristics of myeloproliferative diseases and myelodysplastic syndrome. It strikes older adults, and up to 100,000 individuals are diagnosed every year in the United States alone. It is more common in males and may sometimes appear in young adults.
Hairy cell leukemia (HCL)
It is a type of leukemia affecting lymphocyte creation and maturation, especially B cells. It is a type of blood cancer that progresses very slowly and can be considered a subtype of chronic lymphocytic leukemia. One of the characteristic features of hairy cell leukemia is the form adopted by the aberrant B cells. They display a series of cytoplasmic prolongation similar to villi or hairs, which is why they are called hairy cells.
This disease is more common in older adults and symptoms include recurrent infections, unexplained fever, muscle weakness and chronic fatigue, unexplained and unexpected weight loss, swollen lymph nodes, and easy bruising. There’s more information about hairy cell leukemia in our article devoted to this particular topic.
Juvenile myelomonocytic leukemia (JMML)
It is a relatively uncommon type of blood cancer featuring a rapid progression and typically displaying characteristics of a mixed myeloproliferative and myelodysplastic disease. The onset of juvenile myelomonocytic leukemia is around 6 years old and in younger children. It can be diagnosed in infants, too, and it is more common in males.
Large granular lymphocytic (LGL) leukemia
It is a type of blood cancer that affects lymphocytes, and there are two types of large granular lymphocytic leukemia (LGL) depending on the type of lymphocyte affected by the disease. We can have T cell LGL or natural killer LGL, and they can be both chronic (slow-progressing) or very aggressive. This disease affects men and women equally, and the age of diagnosis is usually 60 years or more.
Blastic plasmacytoid dendritic cell neoplasm
It is a subtype of acute myeloid leukemia often underreported because it is difficult to diagnose. This type of leukemia was formerly known as natural killer lymphoma or natural killer leukemia, and even though there’s not much information about the disease and no established treatment, we know it is more common in men, and the age of diagnosis typically ranged between 60 and 70 years. This type of leukemia features a reduction of red blood cells, white blood cells, and platelets in the blood.
Myeloproliferative neoplasms (MPNs)
Besides leukemia, we have other types of blood alterations associated with the stem cells in the bone marrow. They are known as myeloproliferative neoplasms. They affect the myeloid cell lines, which include red blood cells, white blood cells, and platelets. It is a dysfunction in the bone marrow, and it is subdivided into various types depending on the cell that is being overproduced.
The most important myeloproliferative neoplasms are polycythemia vera, essential thrombocythemia, eosinophilia, and myelofibrosis.
Myelodysplastic syndromes (MDS)
It is a heterogeneous group of diseases with very similar features, and sometimes difficult to differentiate from one another. In all of them, the bone marrow starts to fail in producing enough blood cells. Not only white blood cells are affected. Myelodysplastic syndromes can affect platelets or red blood cells, too, and feature at least one type of cytopenia. Moreover, in myelodysplastic syndromes, the cells found in the bone marrow and the blood do not look normal under the microscope, which gives the disease its name.
Myelodysplastic syndromes are thought to be preleukemic because many patients develop acute leukemia at some point in the disease. There’s much more to learn about this umbrella term in our article about myelodysplastic syndromes.
Systemic mastocytosis (SM)
There are many types of white blood cells, and one of them is called mast cells. These are important to improve healing properties and during the process of immune response and allergies. When too many mast cells build up in the blood, it is called mastocytosis. In systemic mastocytosis, excess mast cells start causing problems throughout the gastrointestinal tract, causing diarrhea, nausea, and vomiting. It is a bone marrow problem, similar to leukemia and myelodysplastic syndromes, so the best way to diagnose is by taking a bone marrow sample and performing a biopsy.
As you have probably seen, leukemia and other syndromes associated with bone marrow dysfunction often feature a reduction of cells in the blood. The signs and symptoms are according to the phase of the disease and the subtype, and the age of onset is quite variable depending on each patient.
References
Gralnick, H. R., Galton, D. A. G., CATOVSKY, D., SULTAN, C., & BENNETT, J. M. (1977). Classification of acute leukemia. Annals of Internal Medicine, 87(6), 740-753.
Loughran, T. P., & Starkebaum, G. (1987). Large granular lymphocytic leukemia. Medicine (Baltimore), 66, 397-405.
Wang, J. C., & Dick, J. E. (2005). Cancer stem cells: lessons from leukemia. Trends in cell biology, 15(9), 494-501.
Aricò, M., Biondi, A., & Pui, C. H. (1997). Juvenile myelomonocytic leukemia. Blood, 90(2), 479-488.
Gilliland, D. G., Jordan, C. T., & Felix, C. A. (2004). The molecular basis of leukemia. ASH Education Program Book, 2004(1), 80-97.