Polycythemia vera (NORD)
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Polycythemia vera (NORD)
Pathology
Anemias
Iron deficiency anemia
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Polycythemia vera (NORD)
Myelofibrosis (NORD)
Essential thrombocythemia (NORD)
Langerhans cell histiocytosis
Mastocytosis (NORD)
Plasma cell dyscrasias
Multiple myeloma
Monoclonal gammopathy of undetermined significance
Waldenstrom macroglobulinemia
Hematological system pathology review
Microcytic anemia: Pathology review
Non-hemolytic normocytic anemia: Pathology review
Intrinsic hemolytic normocytic anemia: Pathology review
Extrinsic hemolytic normocytic anemia: Pathology review
Macrocytic anemia: Pathology review
Heme synthesis disorders: Pathology review
Coagulation disorders: Pathology review
Platelet disorders: Pathology review
Mixed platelet and coagulation disorders: Pathology review
Thrombosis syndromes (hypercoagulability): Pathology review
Lymphomas: Pathology review
Leukemias: Pathology review
Plasma cell disorders: Pathology review
Myeloproliferative disorders: Pathology review
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Polycythemia vera (NORD)
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Polycythemia vera (NORD)
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USMLE® Step 1 style questions USMLE
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| Laboratory value | Result |
| Hemoglobin | 19.0 g/dL |
| Hematocrit | 57% |
| Erythrocytes | 7.2 million/mm3 |
| Leukocytes | 12,900/mm3 |
| Platelets | 440,000/mm3 |
Which of the following additional sets of findings would be expected in this patient?
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Aspirin p. 499
polycythemia vera p. 441
Hematocrit
polycythemia vera p. 441
Hydroxyurea p. 448
polycythemia vera p. 441
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Transcript
Content Reviewers
Rishi Desai, MD, MPHContributors
Evan Debevec-McKenney
Stefan Stoisavljevic, MD
In polycythemia vera, there are increased blood cell levels due to overproduction by the bone marrow, which is a soft tissue found within the bones.
Normally, about 45% of the total blood volume is made up of erythrocytes, or red blood cells, and their main function is to carry oxygen to tissues and bring carbon dioxide to the lungs so it can be expired. This value is called the hematocrit.
In polycythemia vera there’s an increase in red blood cell production.
It typically begins with a mutation in a single hematopoietic stem cell, which gives rise to red blood cells, white blood cells, and platelets.
In 90 percent of the affected individuals there is a mutation of the Janus Kinase 2 or JAK2 gene.
Normally, the kidneys produce erythropoietin which is a hormone that binds to receptors on the hematopoietic stem cells and activates JAK2 gene.
When that happens, it causes the cell to divide and thus produce more blood cells.
However, when there’s a mutation, it keeps JAK2 gene activated, and these cells are able to divide even in the absence of erythropoietin.
The mutated cells proliferate, and rapidly become the predominant hematopoietic cells in the bone marrow.
In time these cells start to die out and that’s when scar tissue forms.
At that point, the bone marrow can no longer produce blood cells, leading to anemia or low red blood cell levels, thrombocytopenia or low platelet levels, and leukopenia or low white blood cell levels. This is known as the spent phase.
And once the disease is in the spent phase, it’s really a different disease altogether - at that point it’s myelofibrosis.
The most common symptoms of polycythemia vera are fatigue, dizziness, increased sweating, redness in the face, blurred vision, and itchy skin especially after a hot shower.
Itchiness develops due to the increased number of basophils and mast cells which contain histamine that causes itching when released.
Summary
Polycythemia vera is a bone marrow disorder in which there is an overproduction of blood cells, often caused by a JAK2 mutation within hematopoietic cells in the bone marrow. It can lead to elevated hemoglobin and hematocrit and predispose an individual to develop blood clots. Symptoms may include fatigue, weakness, headaches, dizziness, itching, and abdominal pain. Treatment may include medications to lower blood cell formation, and prevention of blood clots, phlebotomy, and radiation therapy.
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