September 23, 2015 - Polycythemia

Question 1

Polycythemia

Answer 1

Many “cytes”

High RBC, high platelets, and high WBC

Question 2

Erythrocytosis

Answer 2

High RBC or high hemoglobin

Often confused with polycythemia.

Question 3

Relative Polycythemia

Answer 3

Caused by burns, diarrhea, or dehydration.

Blood plasma levels are decreased, so RBC occupy a higher percentage and appear elevated, even though they are not.

Question 4

High EPO Without Hypoxia

Answer 4

Any decrease in oxygen delivery to the kidney.

• Renal artery stenosis
• High affinity hemoglobin
• Carboxy-HGB (carbon monoxide)

Question 5

High EPO With Hypoxia

Answer 5

Any decrease in oxygenation of arterial blood will cause an increase in EPO. Common causes include…

• High altitude
• Sleep apnea

- Chronic lung disease

• Cyanotic heart diseases

Question 6

Autonomous Bone Marrow Production

Answer 6

Will result in a production of blood cells with a corresponding low EPO.

Bone marrow is highly active. This can be from familial forms (congenital) or can be from polycythemia vera (acquired).

Question 7

JAK-2

Answer 7

Mutated in polycythemia vera.

JH2 no longer inhibits JH1, and the receptor is activated in the absence of EPO binding. This causes it to continuously produce blood cells.

Question 8

Polycythemia Vera

Answer 8

A neoplasm in which the bone marrow makes too many blood cells. Caused by a JAK-2 mutation which causes the receptor to be activated, even in the absence of EPO (which is normally needed for proliferation).

Most of the health concerns occur as a result of the thicker blood.

Question 9

Consequences of Erythrocytosis

Answer 9

• Blood viscosity increase
• Decreased blood flow which results in decreased oxygen delivery which can manifest as headache, confusion, or chest pain
• Vascular dilation which can cause redness or hemorrhage
• Significantly increased risk of thrombosis

Question 10

Clinical Presentation of Polycythemia Vera

Answer 10

Non-specific symptoms such as headache, weakness, dizziness, sweating, gouty arthritis.

Pruritis (particularly aquagenic - feel VERY itchy after getting out of the shower)

Thrombosis

Erythromelagia (burning in hands)

Question 11

Physical Examination of PV

Answer 11

Splenomegaly (mild/moderate)

Facial plethora (redness)

Hepatomegaly

Question 12

PV Lab Features

Answer 12

Elevated Hct - 95%

Thrombocytosis - 60%

Leukocytosis - 40%

Hypercellular bone marrow - 90%

Low/absent iron stores in marrow - 94%

Low EPO - 95%

JAK-2 mutation - 95%

Question 13

PV Treatment

Answer 13

+ Phlebotomy to keep Hct < 0.45

+ Low-dose ASA

+ Hydroxyurea (if platelets >1000 or 60+ years old)

Question 14

Prognosis of PV

Answer 14

6-18 months if untreated

13.5 years if treated