February 2025 Vol 11 No 1
Dr. Lucia Masarova
Polycythemia vera was first recognized by French physician Louis H. Vaquez in 1892 and was known then as maladie de Vaquez.1 The name poly-cyt-[h]emia originates from the Greek and Latin, and literally means many-cells-in the blood. In 1951, Dr. William Dameshek included polycythemia vera in the category of classic Philadelphia chromosome–negative myeloproliferative disorders (now classified as myeloproliferative neoplasms, MPNs; myelo refers to the bone marrow, proliferative refers to rapid growth of blood cells, and neoplasm describes abnormal and excessive growth). It is the only one among the 3 classic MPNs that exhibits erythrocytosis, the increased production of red blood cells. Polycythemia vera is a condition associated with overproduction of all blood cells, including white cells and platelets.
Polycythemia vera is a chronic, incurable disease of the hematopoietic stem cells, the primary cells that can develop into different types of blood cells and are responsible for the production of blood cells during a human’s entire life. It is a clonal disease, meaning it occurs when a mutated hematopoietic stem cell starts making clones—cells with the same genetic mutation. Most affected patients can live a relatively normal and long life.
A breakthrough discovery of a genetic “driver” of polycythemia vera was made in 2005—a mutation in the JAK2 gene was found in 95% of cases, typically JAK2V617F, a mutation that leads to the constitutive activation of the JAK-STAT protein pathway causing unregulated overproduction of hematopoietic cells. This discovery led to improved understanding of the biology, pathogenesis, and long-term behavior of the disease and initiated numerous efforts to develop novel therapies focused on the inhibition of the JAK-STAT pathway.
The abnormal function of the immune system and the subsequent increased inflammation, powerfully driven by the JAK-STAT pathway as the major regulator of inflammatory signaling, contribute to disease progression and an impaired quality of life. Despite the relatively slow progression of the disease course in most patients, the disease possesses its challenges and risks, including a lifetime risk of developing thrombosis (blood clots); the evolution into myelofibrosis, a chronic type of leukemia; or development into acute leukemia. Both blood clots and leukemia are consequences that can shorten life expectancy significantly.