Red blood cells, a type of cell found in the blood, carry oxygen all throughout the body. When these cells grow in number beyond what is required, the blood thickens, restricting oxygen flow. This is what happens in polycythemia vera. The condition affects the bone marrow, making it produce excess red blood cells. Knowing why polycythemia vera develops and the common risk factors can help one seek the right treatment and recover.

Polycythemia vera – What causes it?

The main cause of polycythemia vera lies deep inside the body, particularly in the JAK2 gene found in the bone marrow’s stem cells. The stem cells within the bone marrow produce red blood cells. Under normal circumstances, the JAK2 gene sends signals to the bone marrow only when the body needs more red blood cells. However, in polycythemia vera, a mutation occurs that changes how this gene functions. As a result, the gene continuously signals for red blood cell production, even when the body does not need more. 

A change in the JAK2 gene is observed in most cases of polycythemia vera. The mutated gene activates a protein that increases cell growth in the bone marrow. As a result, red blood cells rapidly increase in number, and the blood starts to thicken. In rare cases, however, another gene called TET2 can also mutate alongside JAK2. These TET2 mutations can cause similar problems with red blood cell production.

What happens in polycythemia vera?

The bone marrow lies deep within the bones and works like the body’s blood cell factory. The stem cells in the marrow get signals from the body and produce the right amount of red blood cells, white blood cells, and platelets. These cells, present in balanced proportions, keep the blood flowing continuously, delivering oxygen and fighting infections.

This scenario changes in polycythemia vera. The mutated stem cells cause red blood cells to be produced faster. These extra cells begin to overcrowd the blood, leading to an imbalance. The result is thick, sluggish blood packed with too many red cells.

Sometimes, there is an increase in the number of white blood cells and platelets, too, which can cause further imbalance. These changes happen slowly over time, affecting how blood flows through the veins and arteries.

As the red cells multiply and the blood thickens, someone with polycythemia vera begins to experience various symptoms.

• Headaches or dizziness because of reduced blood flow
• Fatigue and weakness with less oxygen delivered to various organs
• Itching, especially after contact with warm water
• Shortness of breath during routine activities
• Blurred vision or blind spots
• Numbness or tingling in hands and feet

Polycythemia vera – Risk factors

In most cases of polycythemia vera, mutations in the stem cells occur during one’s lifetime. These are known as acquired somatic mutations. The changes occur in bone marrow stem cells after birth and are not generally passed down from parents. In rare cases, though, family patterns can appear. One may carry a higher risk of the condition at birth if their parents have an autosomal dominant trait. 

The exact trigger for this genetic mutation is still not known. Something in the body triggers the mutation, but there has been no conclusive research on the underlying causes of polycythemia vera. 

If one experiences the symptoms of the condition, they should work closely with a healthcare professional and seek treatment. The professional may suggest a treatment option based on one’s age, risk profile, risk of clots, and other factors.