This page was reviewed under our medical and editorial policy by
Haris Ali, MD, Hematologist-Oncologist, City of Hope | Duarte
Karamjeet Singh Sandhu, MD, Hematologist-Oncologist, City of Hope | Duarte
This page was updated on June 19, 2023.
Once referred to as myeloproliferative disorder, myeloproliferative neoplasms (MPNs) are a group of diseases in which the bone marrow makes too many red blood cells, platelets or white blood cells. MPN is a rare type of blood cancer.
According to the Leukemia & Lymphoma Society, around 20,000 people in the United States are diagnosed with a myeloproliferative neoplasm each year, and about 295,000 people are living with the disease.
The main types of myeloproliferative neoplasms under the latest World Health Organication (WHO) classification are:
The unique characteristic of these conditions is that they have a driver gene mutation, which is responsible for cytokine-independent growth and overproduction of blood cells. This also causes a variety of symptoms, as described below in detail. These diseases become more challenging as the number of cells build up in the bloodstream and/or bone marrow and in some cases may be a precursor to leukemia.
This overview will cover the basic facts about MPNs, including:
MPNs are classified into subtypes based on:
There are several types of MPNs:
CML: This is a slowly progressing disease that occurs when the bone marrow makes too many white blood cells, and it may not have any symptoms initially. A genetic mutation called the Philadelphia chromosome is typically found in the blood cells of CML patients.
PV: This condition occurs when too many red blood cells are produced in the bone marrow. Symptoms may include headaches, itching after bathing, reddened skin and/or fullness below the ribs on the left side. Genetic changes in the JAK2 gene are present in the vast majority of patients. This can evolve to myelofibrosis or acute leukemia.
PMF: This condition is characterized by abnormal blood cells and fibers in bone marrow. Symptoms may include pain below the ribs on the left side due to spleen enlargement and extreme fatigue. PMF may be caused by a genetic change to the JAK2 gene, MPL gene or CALR gene. Sometimes, PV and ET may progress to myelofibrosis, which is also called secondary MF.
ET: This condition is characterized by too many platelets in the bone marrow. With this type of condition, symptoms aren’t always present. Complications related to blood clots or bleeding could be what initially prompts patients to see the doctor. Essential thrombocythemia may be caused by a genetic change to the JAK2 gene, MPL gene or CALR gene. This can evolve to myelofibrosis or acute leukemia.
Chronic neutrophilic leukemia: In this condition, too many blood stem cells morph into a type of white blood cell known as neutrophils. When too many neutrophils form, the spleen and liver may swell. This disease may progress quickly to acute leukemia.
Chronic eosinophilic leukemia: In this disease, too many white blood cells, called eosinophils, are produced in the bone marrow. Symptoms may be related to deposits of eosinophils in the organs, and may include skin rashes, trouble breathing and impaired mobility.
MPN-U: These are MPNs that showcase some clinical, morphological or molecular features of myeloproliferative neoplasms, but they don’t fit in any of the subtypes listed above. MPN-Us make up approximately 5 percent to 10 percent of all myeloproliferative neoplasms.
Risk factors for MPNs include:
MPNs may not cause symptoms in the beginning. Oftentimes, people are diagnosed following a routine blood test. Symptoms may not be noticeable for months or years after a diagnosis.
However, if symptoms do develop, they may include:
In general, diagnosing MPNs involves blood testing and biopsy, including:
Treatment for MPNs is based on the specific type of disease, whether or not it is causing symptoms, and a person’s overall health status. Possible treatments for MPNs include:
Watchful waiting: Not all cases of MPNs will need treatment. Sometimes doctors will monitor for signs of symptoms of progression.
Targeted therapy: These drugs "target" specific cancer cells without affecting normal cells. Tyrosine kinase inhibitor (TKI) therapy, for example, blocks driver signals that cause cancer cell growth. ABL1 inhibitors in CML and JAK STAT inhibitors in PV and PMF may decrease elevated blood cell numbers, improve the size of the spleen and modulate the response of proteins playing a role in symptoms related to PV and certain types of myelofibrosis. In cases of CML, it may cause long-term remission.
Phlebotomy: A phlebotomy may be used to remove extra red blood cells and reduce the risk of a blood clot in polycythemia vera.
Transfusion therapy: Blood transfusions may be used to replace blood cells due to decreased production as a result of the disease or destruction as a result of cancer treatment.
Chemotherapy: These drugs are used to kill cancer cells or stop them from multiplying.
Radiation therapy: Radiation therapy uses high-energy X-rays or other types of radiation to kill cancer cells.
Surgery: A surgeon may remove the spleen (via a splenectomy) if it’s enlarged.
Immunotherapy: Immunotherapy is used to shut down key proteins on immune cells that allow the cancer to go undetected by the body’s immune system. Interferon alfa and pegylated interferon alpha are commonly used immunotherapy drugs for some MPNs.
Stem cell or bone marrow transplant: This is currently the only potential curative treatment option in the majority of MPN diagnoses. It is, in essence, an immunotherapy. Stem cells are removed from the blood or bone marrow of healthy donors and infused to the patient (after treatment that destroys underlying MPN-causing cancer stem cells) so they can grow into healthy blood cells. For some types of MPNs, the procedure is preceded by high-dose chemotherapy.
Some treatments are used to reduce and manage symptoms.
For anemia, these medications may be recommended:
Anti-platelet agents may also reduce the risk of blood clots. Clinical trials with novel agents are encouraged, as they may help treat patients.
A staging system hasn't been developed specifically for chronic myeloproliferative neoplasms as it has for solid tumors and lymphomas, because the MPN subtypes listed above each behave differently. Knowing the type of MPN helps physicians plan treatment. Each subcategory has a different prognostic scoring system to estimate prognosis and help determine treatment, so always talk to the care team about specific survival data and prognosis information.
Differences in survival are based on the type of disease: