Dr. Hersh: This disease causes the bone marrow to make too many red blood cells

Q: My friend says his uncle is being treated for a disease where he has too much blood and he gets “bloodletting’” every other day, like in the Middle Ages. Is there really such a thing, or is he being dramatic?

A: If by bloodletting you mean “removal of some of a patient’s blood for therapeutic purposes” — what we now call therapeutic phlebotomy — then yes, this is an actual treatment for, among other things, the following:

• Hemochromatosis, a condition where iron levels build up in the body to dangerous levels, or other conditions that may cause a dangerous buildup of iron such as hyperferritinemia in patients with nonalcoholic fatty liver disease. 
• Porphyria cutanea tarda, a genetic condition that causes a defect in one of the heme synthesizing enzymes (heme is an iron-containing compound that’s needed to form hemoglobin, the part of the red blood cells that carries oxygen to distribute it to the cells of the body).
• Polycythemia vera, which might best fit the description you give of “having too much blood,” and hence is the topic of today’s column.

What is Polycythemia vera?

Polycythemia vera (PV) is a type of blood cancer that causes the bone marrow to make too many red blood cells; it occurs in about 1 in a million people. The bone marrow is where red blood cells, platelets (which help stop bleeding by forming a clot to “plug up” damaged blood vessels, other functions), white blood cells (which help detect and fight infections and other body “invaders” such as certain toxins/foreign molecules, and are a key part of the overall immune system) and stem cells are made.

The most prominent feature of PV is an increase in the production of red blood cells, although all cells made in the bone marrow are often over-produced — and are hence elevated from normal levels. The hematocrit is the ratio of the total volume of blood to the total volume of red blood cells, so in PV the hematocrit is elevated. In fact, the most common way PV is suspected is when a complete blood count is done for any reason, and the hematocrit is found to be elevated.

Physical exams demonstrate an enlarged spleen in 75% of PV patients (understandable, as the spleen acts to filter out old, deformed and damaged blood cells), and an enlarged liver in about one-third.

What are the symptoms of Polycythemia vera?

PV may cause several symptoms, including itching, headache, dizziness, changes in vision, ringing in the ears, claudication, angina, high uric acid levels and gastrointestinal symptoms.

Even more concerning is the increased risk for certain complications, specifically thrombosis (formation of blood clots that may block blood vessels and cause compromised blood supply to the tissues/organs those blood vessels ‘feed’, called ischemia), bleeding, as well as increased blood thickness due to the increased volume of red cells, which can also lead to impaired blood flow.

In addition, progression to myelofibrosis or leukemia is also a concern.

Tests to evaluate possible PV include a CBC, oxygen saturation levels, a bone marrow biopsy, genetic testing and erythropoietin (the hormone that stimulates the bone marrow to make red blood cells) levels. Per the World Health Organization, the diagnosis of PV is made based on results of these tests. Other blood tests, such as measuring uric acid, leukocyte alkaline phosphatase, and others, may also be indicated.

How is Polycythemia vera treated?

The overall treatment goal for PV is tailored for each individual patient to reduce their risk of the compilations above and to relieve symptoms, all while minimizing the risk of their PV transforming into leukemia or myelofibrosis.

The initial treatment is usually periodic therapeutic phlebotomy to lower the hematocrit to a normal level and maintain it (it’s not uncommon that patients need this up to every other day), and a baby aspirin to help prevent thrombosis.

Many patients will also require medication to slow down red blood cell production, with hydroxyurea being the most commonly used agent. Other medications may be needed in select patients who do not respond to these treatments, although care must be taken as some may increase the risk of the patient’s PV transforming into leukemia, myelofibrosis and/or developing other complications. Specific issues such as a bleeding ulcer, complications from a severely enlarged spleen, etc. may require surgical intervention.

Untreated, PV is usually fatal within one to two years. But with appropriate therapy, survival is typically at least 10-15 years with an average survival of about 20 years. 

Jeff Hersh, Ph.D., M.D., can be reached at[email protected].