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Myeloproliferative neoplasms (MPNs) are cancers of the blood and bone marrow. Before the World Health Organization (WHO) reclassified this group of blood cancers in 2008, they were known as myeloproliferative disorders. MPNs have many features in common with other types of blood cancer such as leukemia, lymphoma, and multiple myeloma. In some cases, different types of MPNs and other blood cancers are related in complex ways.
MPNs develop when blood stem cells in the bone marrow grow and reproduce abnormally. Abnormal growth has two results: too many of one or more types of blood cells and blood cells that do not work properly.
There are three main types of blood cells:
All of these blood cells come from stem cells in the bone marrow. Stem cells are immature cells that have the potential to develop into any of the three main types of blood cells.
Symptoms of MPNs can vary depending on the type, and some people may not notice any signs in the early stages. In many people, an MPN is diagnosed after a routine blood test. Others may go to their doctor after noticing symptoms, leading to tests and a diagnosis of MPN.
MPNs are considered progressive conditions. In many cases, MPNs develop slowly over time. In rare instances, MPNs can develop rapidly and transform into acute myeloid leukemia (AML).
MPNs may be classified in different ways. One main distinction is which blood cells are produced in excess — red blood cells, one or more types of white blood cells, platelets, or multiple types of cells.
Another consideration is which genetic mutations (changes) are present. Like most cancers, MPNs develop when changes in DNA cause the uncontrolled growth of cells. Some mutations may be inherited from parents, while others occur randomly during fetal development, and still others are acquired throughout a lifetime. Knowing which mutations you have helps doctors better understand which treatment options for MPNs are likely to be most effective.
Read more about inherited and environmental risk factors for MPNs.
Three types of myeloproliferative neoplasms are considered to be classic:
In polycythemia vera (PV), too many red blood cells are produced in the bone marrow. In rare cases, PV can transform into AML.
Extra RBCs make the blood thick, raising the risk of dangerous blood clots, stroke, or heart attack. The spleen becomes enlarged as it tries to remove the excess RBCs, causing pain or a full feeling on the left side of the abdomen. Other common symptoms of PV include itching, reddened skin, blurry vision, tinnitus (ringing in the ears), and headaches.
PV is more common in older adults and usually shows up around age 60. Roughly 95 percent of people with PV have a JAK2 gene mutation.
If the bone marrow makes too many platelets, they enter the bloodstream and disrupt normal blood clotting. This condition is called essential thrombocythemia (ET). ET can cause unusual blood clots and sometimes bleeding. In rare cases, it can develop into myelofibrosis or acute leukemia.
Early in the course of ET, people may not show any symptoms. As the condition progresses, they may experience headaches, vision or hearing problems, enlarged spleen, burning pain in the hands, and tingling or numbness in the hands or feet. Overproduction of platelets may lead to clotting, increasing the risk for a serious health event, such as a heart attack or a stroke. Conversely, very high levels of platelets may also lead to bleeding symptoms, such as nosebleeds, bruising easily, or bloody stool.
MPN Research Foundation states that ET is most commonly diagnosed in women over the age of 50. In addition, 50 percent of those with ET have a JAK2 gene mutation.
Also known as PMF or chronic idiopathic myelofibrosis, primary myelofibrosis (MF) happens when fibrosis (scarring) in the bone marrow makes it harder for the body to produce red blood cells and granulocytes (a type of white blood cell). In MF, RBCs and granulocytes develop abnormally, have irregular shapes, and do not function effectively. As fibrosis progresses, the bone marrow produces too few blood cells. MF can develop on its own or as a result of PV (in 15 percent of PV cases) or ET. MF can be divided into two stages: prefibrotic (early stage) myelofibrosis and overt fibrotic (advanced stage) myelofibrosis. MF rarely transforms into AML.
Common symptoms of MF include fatigue, shortness of breath, weakness, enlarged spleen, easy bruising or bleeding, and frequent infections.
MF is most often diagnosed in people over age 60. Between 50 percent and 60 percent of those with MF have a JAK2 gene mutation, 5 percent to 10 percent have a mutation of the MPL gene, and some have a genetic mutation called CALR.
Several other types of blood cancers fall under the category of MPNs, and some are also considered types of leukemia:
CML may be referred to as either CML or chronic myelogenous leukemia. In CML, the bone marrow produces large numbers of white blood cells called granulocytes. The abnormal white blood cells build up in the bone marrow, making it hard for the body to produce healthy blood cells of all types. CML cells are also abnormal and can’t effectively protect the body from infections.
In the chronic phase of CML, the disease progresses slowly, and most people have mild or no symptoms. During this stage, the body is still able to produce some healthy blood cells, and treatment is often effective at keeping the condition under control.
In most people with CML, cancer cells are Philadelphia-positive. That is, the CML cells have the Philadelphia chromosome — a genetic abnormality named after the city where it was discovered — where part of chromosome 22 switches places with part of chromosome 9. Some cancers are classified as Philadelphia-positive or Philadelphia-negative, based on whether the chromosome is present. The terms “BCR-ABL-positive” and “BRC-ABL-negative” may also be used, because they refer to the specific genes that are disrupted by the mutation. The three classic MPNs are Philadelphia-negative.
Symptoms of CML include fatigue, weakness, bleeding, and bruising easily. Symptoms may also include fever and night sweats.
About 70 percent of people diagnosed with CML are over the age of 40. CML is more common in men, per the Leukaemia Foundation.
In CNL, there is an excess of neutrophils in the blood and bone marrow. CNL can progress to AML and is very rare. The WHO has found that only about 200 people have been diagnosed with CNL since it was discovered in 2001.
People with CNL don’t usually have symptoms early on in the disease. However, as the disease progresses, the spleen and liver may become enlarged. People may also experience fatigue, night sweats, and fever.
Also known as systemic mast cell disease, mastocytosis is a rare disorder in which mast cells accumulate in the bone marrow, skin, or gastrointestinal tract. There are many subtypes of mastocytosis. Mast cells are part of the body’s response to parasites, but they are best known for their role in allergies. Mast cells release histamine in the body, triggering itching, abdominal cramping, or anaphylaxis — a life-threatening allergic response. Mastocytosis is the result of an acquired genetic change in a protein called c-kit. National Organization for Rare Disorders reports that more than 90 percent of adults and more than 40 percent of children with mastocytosis have this mutation.
Symptoms of mastocytosis vary widely by the subtype of the condition. They can include a variety of skin lesions, enlarged spleen, gastrointestinal symptoms, and loss of bone density.
Mastocytosis can affect adults and children. For many children, it starts in the first two years of life but often resolves in puberty. Children typically develop mastocytosis in the skin. Adults may develop the condition in the bone marrow and skin.
CEL occurs when the body produces too many eosinophils. CEL can quickly progress to AML and is rare.
Common symptoms of CEL are fever and fatigue. In addition, some people experience swelling around the lips or eyes, itching, and swollen hands or feet.
Any abnormal production of blood cells in the bone marrow that doesn’t fit into one of the types previously described falls into this category. Symptoms for MPN, unclassifiable, include fever, weight loss, and fatigue.
On myMPNteam, the social network for people with myeloproliferative neoplasms and their loved ones, more than 4,700 members come together to ask questions, give advice, and share their stories with others who understand life with MPNs.
Have you had symptoms that suggest your myelofibrosis is progressing? Which symptoms appeared first? Share your experience in the comments below, or start a conversation by posting on your Activities page.
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I have managed my diagnosis of polycythemia by exercising and diet. Diagnosed when I was 50. Twenty years ago.
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