AssessmentsPolycythemia vera (NORD)
Polycythemia vera (NORD)
USMLE® Step 1 style questions USMLE
A 58-year-old female comes to her outpatient provider’s office for symptoms of fatigue, headaches, and pruritus that is worse with showering. The symptoms began three months ago. The patient consumes half-a-pack of cigarettes per day, has a 30-pack-year smoking history, and drinks 3-4 beers per week. Her temperature is 37.0°C (98.6°F), blood pressure is 120/73 mmHg, pulse is 71/min, and respiratory rate is 14/min. On physical exam, the patient is observed to have a reddish face. Cardiac and pulmonary exams are non-contributory. Abdominal examination reveals an enlarged spleen. Laboratory testing is ordered and the results are as follows:
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?
Content Reviewers:Rishi Desai, MD, MPH
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.
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.