Polycythemia vera (PV)

What is polycythemia vera (PV)?

Polycythemia vera (PV) is one of a related group of blood cancers known as “myeloproliferative neoplasms” (MPNs), occurring when too many red blood cells are made in the bone marrow and, in many cases, the numbers of white blood cells and platelets are also elevated.

With careful medical supervision, PV can usually be managed effectively for many years. For some PV patients, however, the PV may progress to a more aggressive blood disease, such as myelofibrosis (MF), acute myeloid leukemia (AML), or myelodysplastic syndromes (MDS).

You should be treated by a hematologist-oncologist, a specialist who treats people who have PV or other types of blood cancer. PV is a chronic disease: It is not curable, but it usually can be managed effectively for long periods. Medical supervision of individuals with PV is important to prevent or treat complications. 

What should I do if I am diagnosed with PV?

• Talk with your doctor about your diagnostic tests and what the results mean
• Talk with your doctor about all your treatment options, side effects, and the results you can expect from treatment
• Ask your doctor whether a clinical trial may be a good treatment option for you
• Find a blood cancer specialist or treatment center

How does PV develop? 

Stem cells form blood cells (white cells, red cells, and platelets). The DNA (genetic material) of a developing stem cell in the bone marrow undergoes a change (genetic mutation).   

The mutated cell leads to uncontrolled blood cell production, especially red cells.  In many cases, the numbers of white blood cells and platelets are also elevated. With extra blood cells in the bloodstream, abnormal clots and bleeding are more likely to occur. 

This can increase the risk of: 

• Heart attack and/or stroke (a clot that blocks blood flow to part of the brain which can damage brain tissue)
• Pulmonary embolism (blockage of an artery in the lungs)
• Accumulation of extra blood cells in the spleen, causing the spleen to swell  

PV disease complications 

In medicine, a complication is a medical problem that occurs during the course of a disease or after a procedure or treatment.  

Possible complications of PV include: 

Thrombus (Blood clot) 

The extra blood cells in people with PV may cause the blood to be thicker than normal. As a result, harmful blood clots may form and block the flow of blood through arteries and veins. Blood clots that form in an artery can lead to a heart attack or a stroke.  

They can also form in the deep veins of the arms or legs, a condition called “deep vein thrombosis.” If a blood clot from a deep vein breaks loose and travels to the lungs, it can become lodged in the lungs and block blood flow, which can be life threatening. This is called a “pulmonary embolism.”  

Bleeding 

Patients with PV may develop acquired von Willebrand disease, a clotting disorder that puts them at a high risk of bleeding.  

Enlarged spleen 

The spleen is an organ located on the left side of the upper abdomen, near the stomach and below the rib cage. It filters the blood, stores blood cells, and destroys old blood cells. In some people with PV, the spleen may become abnormally enlarged because it is working harder to manage the increased number of blood cells.  

An enlarged spleen can cause discomfort or pain in the abdomen. When the spleen pushes up against the stomach, it may also cause a feeling of being full along with a decreased appetite. 

Portal hypertension  

Normally, blood flow from the spleen enters the liver through a large blood vessel called the portal vein. When the spleen is enlarged, increased blood flow through the portal vein can lead to high blood pressure in the vein. This can force excess blood into smaller veins in the stomach and esophagus, potentially causing the veins to rupture and bleed. Portal hypertension may also be caused by a blood clot that develops in the portal vein, which may obstruct the blood flow through it.  

Extramedullary hematopoiesis  

When the bone marrow is no longer able to make sufficient blood cells, other organs in the body such as the spleen may begin to produce blood cells. This often causes the spleen and liver to become enlarged. Extramedullary hematopoiesis may also lead to the creation of clumps or tumors of developing blood cells in other areas of the body, which may cause bleeding in the gastrointestinal (GI) system, coughing or spitting up blood, compression of the spinal cord, or seizures.  

Other blood diseases

In some cases, PV may progress to other related blood diseases including myelofibrosis (MF), acute myeloid leukemia (AML) and, less commonly, myelodysplastic syndrome (MDS). 

 Find facts and statistics about PV and other blood cancers.

Source: Myeloproliferative Neoplasms. Reviewed by John Mascarenhas, MD.