Why Does Polycythemia Vera Cause Leg Pain?

Polycythemia vera (PV) is a blood cancer that occurs when the body creates too many red blood cells. When a patient with PV experiences leg pain, this may be a red flag. In some cases, leg pain is benign and may be unrelated to PV, but it can also indicate a life-threatening emergency. Understanding the connection between leg pain and PV is essential, as well as knowing when to seek medical attention.

“There can be many causes of leg pain with polycythemia vera,” said Angela Fleischman, MD, PhD, Assistant Professor in the Department of Medicine, Division of Hematology/Oncology at UC Irvine Health. “MPNs can cause bone pain from hyperactive bone marrow. Deep vein thromboses can also cause leg pain.”

You may already know myeloproliferative neoplasms (MPNs) are a group of blood cancers that affect the red blood cells, white blood cells, and platelets, and that PV is an MPN that increases the number of red blood cells to abnormal levels. But did you know this thickens the blood? Joseph Scandura, MD, PhD, associate professor of medicine at Weill Cornell Medicine, described this thickening as a traffic jam.

“If you think of the blood vessels in your body as highways, they can only accommodate a certain amount of traffic,” Dr. Scandura explained during a Patient Power program called “What Does ‘Thick Blood’ Mean? Mitigating Risk for Strokes and Clots in PV Patients.” “Sometimes there are too many people trying to get on the highway, and that slows everything down. That’s what’s happening with polycythemia vera. Too many red blood cells are being produced, and they end up causing traffic jams in the blood vessels.”

Thick blood increases the risk of blood clots. If you have thick blood due to PV, your hematologist may recommend phlebotomy to reduce your red blood cell levels and overall blood volume. Phlebotomy is a common treatment option for polycythemia vera. The process is similar to donating blood.

If a blood clot develops in a vein deep within the body, it iscalled deep vein thrombosis (DVT). People with PV have a high risk of DVT due to thick blood. DVT blood clots generally occur in the legs but can also develop in the arms or pelvis. They may cause leg pain, but not always.

DVT symptoms include:

• Unexplained swelling in your leg or arm

• A warm sensation in your skin

• A change in skin color, usually red or purple

• Unexplained leg pain, cramping, or soreness

If a DVT blood clot travels through the bloodstream from your leg, arm, or pelvis to your lungs, it can create an urgent and life-threatening condition called pulmonary embolism (PE).

PE symptoms include:

• Sudden shortness of breath

• Chest pain

• Feeling dizzy or lightheaded

• Rapid or irregular heartbeat

• Pain or swelling in the affected leg

• Coughing (blood may be present)

• A sudden drop in blood pressure

• Sweating

Pulmonary embolism is a medical emergency. If you suspect that you or someone you love is experiencing PE, seek immediate medical assistance.

Sometimes leg pain with PV is caused by a leg cramp that is unrelated to the disease. Common causes of leg cramps include dehydration, overexertion during exercise, electrolyte imbalance, certain medications, and inactivity. To reduce the risk of leg cramps, drink plenty of liquids, move your body, and stretch before and after physical activity.

Treating leg pain with PV is not a one-size-fits-all approach. “It depends on what is causing the pain,” Dr. Fleischman explained. “I would treat the cause.” To help your doctor determine the source of your pain, consider taking notes on what symptoms you feel and when.

To prevent leg pain before it happens, Dr. Fleischman recommends:

• Keeping your hematocrit (HCT) level below 45% to reduce the risk of blood clots

• Getting regular exercise (but talk to your doctor before starting a new exercise program)

• Maintaining a healthy weight

For more information about polycythemia vera lab values and how to lower your HCT level, talk to an MPN specialist.

If you have PV and leg pain, you may wonder when it is appropriate to seek medical care. Dr. Fleischman recommends seeing your doctor if you experience “acute leg pain associated with redness” and “swelling in one leg but not the other.” She also cautions against assuming the worst, so try to avoid diagnosing yourself online.

“I want to emphasize that there can be many causes of leg pain in people with and without PV,” Dr. Fleischman explained. “Blood clots are one cause, but someone with PV and leg pain shouldn’t necessarily jump to the conclusion that they have a blood clot.” When in doubt, talk to your doctor.