Polycythemia vera (PV) is a rare, chronic blood disorder classified as a myeloproliferative neoplasm, meaning it originates in the bone marrow. It is characterized by the overproduction of red blood cells, and often white blood cells and platelets. This increase in blood cells makes the blood thicker, which can hinder proper blood flow and elevate the risk of complications like blood clots. Early diagnosis of polycythemia vera is important for effective management and to prevent serious health issues.
Recognizing Potential Signs
The initial clues suggesting polycythemia vera often involve non-specific symptoms that develop slowly. Individuals may experience fatigue, headaches, dizziness, and blurred vision. Itching, particularly after exposure to warm water like a bath or shower, is a common complaint, potentially linked to abnormal histamine release. Some people also report numbness, tingling, burning, or weakness in their hands or feet.
Physical examination can reveal additional signs. A ruddy or reddish complexion is characteristic of PV. An enlarged spleen, known as splenomegaly, is a common finding as the spleen works harder to filter excess blood cells. An enlarged liver, or hepatomegaly, may also be observed.
Key Laboratory Investigations
The diagnostic process for polycythemia vera relies on specific laboratory tests that reveal characteristic blood abnormalities. A Complete Blood Count (CBC) is a fundamental test, typically showing elevated levels of red blood cells, hemoglobin, and hematocrit. The CBC often indicates an elevated white blood cell count (leukocytosis) and an increased platelet count (thrombocytosis).
Another important blood test measures erythropoietin (EPO), a hormone that stimulates red blood cell production. In polycythemia vera, EPO levels are typically low, unlike secondary polycythemia where EPO levels are often normal or high. A genetic mutation in the JAK2 gene is a hallmark of polycythemia vera. The JAK2 V617F mutation is common, and other JAK2 mutations are also found. Detecting these mutations is an important step in confirming the diagnosis and differentiating PV from other blood disorders.
Bone Marrow Analysis
A bone marrow analysis, including a biopsy and an aspirate, provides important confirmatory evidence for polycythemia vera. This procedure typically involves taking samples from the hip bone. Pathologists examine the bone marrow samples under a microscope to identify specific changes characteristic of PV.
The bone marrow in PV patients often shows hypercellularity, meaning it is unusually active and contains an increased number of blood-forming cells. There is often proliferation across all three blood cell lines—red blood cells, white blood cells, and megakaryocytes, which produce platelets. Pathologists also look for abnormalities in the size and shape of megakaryocytes, which can appear enlarged or clustered. Reticulin fibrosis, an increase in fibrous tissue within the bone marrow, can also be observed, particularly in later stages.
Establishing a Definitive Diagnosis
Reaching a definitive diagnosis of polycythemia vera involves integrating findings from symptoms, physical examination, blood tests, and bone marrow analysis. Healthcare providers use established diagnostic criteria to guide this process. These criteria consider elevated red blood cell parameters, the presence of JAK2 mutations, and specific bone marrow characteristics.
It is important to differentiate polycythemia vera from other conditions that can cause similar blood abnormalities. For example, secondary polycythemia, where red blood cell counts are high due to an underlying condition, typically presents with normal or high erythropoietin levels, unlike PV’s low levels. Essential thrombocythemia, another myeloproliferative neoplasm, primarily involves an increase in platelets, though it can also be associated with the JAK2 V617F mutation. By evaluating all available information and ruling out other causes, a conclusive diagnosis of polycythemia vera can be made, allowing for appropriate management and care.