From the Guidelines
An elevated Red Blood Cell (RBC) count is called polycythemia or erythrocytosis. This condition occurs when the body produces too many red blood cells, resulting in thickened blood that can flow less easily through blood vessels and organs. According to the most recent and highest quality study 1, polycythemia can be classified as primary (caused by genetic mutations affecting blood cell production, as in polycythemia vera) or secondary (resulting from underlying conditions like lung disease, heart disease, or living at high altitudes where oxygen levels are lower).
The diagnosis of polycythemia vera (PV) requires the presence of increased hemoglobin, hematocrit, or red cell mass, and the presence of a JAK2 mutation, along with at least one minor criterion, such as MPD-consistent bone marrow histology, serum erythropoietin level below the reference range for normal, and presence of endogenous erythroid colonies 1. The increased blood viscosity from polycythemia can lead to complications such as blood clots, stroke, or heart attack. Symptoms may include headache, dizziness, fatigue, itchy skin, and a ruddy complexion.
Diagnosis typically involves a complete blood count (CBC) showing elevated hemoglobin, hematocrit, and red blood cell count. Treatment depends on the underlying cause and may include phlebotomy (blood removal), medications to reduce blood cell production, or addressing the primary condition causing the elevated RBC count. It is essential to note that repetitive phlebotomies can deplete iron stores and may result in production of iron-deficient red blood cells, which is undesirable due to the reduced oxygen-carrying capacity and deformability of red blood cells 1.
Key points to consider in the diagnosis and management of polycythemia include:
- Elevated hemoglobin, hematocrit, and red blood cell count on CBC
- Presence of JAK2 mutation and at least one minor criterion for PV diagnosis
- Risk of complications such as blood clots, stroke, or heart attack
- Importance of iron replacement in cases of iron deficiency
- Potential need for phlebotomy, medications, or addressing underlying conditions in treatment.
From the Research
Elevated Red Blood Cell Count
- An elevated Red Blood Cell (RBC) count is called erythrocytosis 2, 3.
- Erythrocytosis can be classified as primary or secondary, and congenital or acquired 3, 4.
- Primary erythrocytosis is caused by a defect intrinsic to the erythroid progenitor cells, while secondary erythrocytosis is caused by circulating serum factors, typically erythropoietin 5, 3.
- Polycythemia vera (PV) is a primary acquired disorder characterized by an increased red blood cell mass and is the most common primary acquired disorder 2, 3.
Diagnosis and Investigation
- The diagnostic criteria for PV have evolved over time, and measurement of the erythropoietin level is a first step in exploring the cause of erythrocytosis 3.
- A low erythropoietin level indicates a primary cause, while a normal or elevated level indicates a secondary etiology 3.
- Further investigation is then dictated by initial findings and includes mutational testing, bone marrow biopsy, scans, and further investigation as indicated by history and initial findings 3, 4.
Types of Erythrocytosis
- Absolute erythrocytosis is present when the red cell mass is greater than 125% of the predicted 3.
- Relative erythrocytosis occurs when there is a decrease in plasma volume, which can be caused by dehydration or other factors 4.
- Idiopathic erythrocytosis is a type of erythrocytosis where the cause is unknown 4.