Quesmed (polycythaemia) Flashcards
What is polycythemia?
An increase in haematocrit, red cell count and haemoglobin concentration.
What is haematocrit?
The ratio of the volume of red blood cells to the total volume of blood.
What is the underlying gene mutation associated with polycythemia?
JAK 2 mutation
What are the 2 main types of polycythemia?
Can be relative or absolute
What is relative polycythemia?
AKA pseudopolycythemia
Occurs when haemoglobin is elevated secondary to low plasma volume rather than low red cell number.
What can relative polycythemia be seen in?
Dehydration
Diarrhoea and vomiting
Excess diuretic use
Fever
Chronic alcohol intake
What is absolute polycythemia?
If the plasma volume is normal, polcythemia is absolute (meaning red cell number would be raised).
What are the 2 types of absolute polycythemia?
Primary and secondary
What is primary absolute polycythemia?
Excess and uncontrolled erythocytosis (high RBC count) that is independent of erythropoietin (EPO) levels
How does the JAK 2 gene mutation influence polycythemia?
Mutations of the JAK 2 gene leads to uncontrolled production of blood cells (especially RBC’s).
What is secondary absolute polycythemia?
Excess RBC production which is driven by raised EPO levels.
When is secondary absolute polycythemia typically seen?
- Situations causing an appropriate rise in EPO i.e. chronic hypoxia (e.g. COPD or long times spent at high altitudes)
- Anabolic steroid use
What are the specific primary features of primary polycythemia (raised RBC count independent of EPO levels)?
Hyperviscosity syndrome: chest pain, myalgia, weakness, headache, blurred vision and loss of concentration.
“Ruddy” complexion: red complexion and reddening of palms and soles, ear lobes, mucous membranes and eyes.
Splenomegaly
What investigations are done for polycythemia?
FBC (Hb raised, raised WCC and platelets)
JAK 2 mutation (>95% cases)
Possible raised urate and impaired renal function.
How can CML be distinguished from polycythemia?
Can exclude CML by doing cytogenic testing to check for “philadelphia” chromosome which is the translocation of chromosomes 9 and 22.
What is venesection?
Effective method of lowering erythrocyte count rapidly.
Treatment options for polycythemia?
- Carry out regular venesection
- Aspirin 75mg daily
- Cytoreductive therapy - suppresses erythropoietin in those where venesection is not effective or those with thrombosis risk.
What are the options for cytoreductive therapy in polycythemia?
1st line: hydroxycarbamide - suppresses erythropoietin and causes macrocytosis.
2nd line: interferon, JAK 2 inhibitors (ruxolitinib)
3rd line: busulfan can be used if leukaemia risk
Hydroxycarbamide is first line for polycythemia in younger patients. True/false?
False
Interferon is usually first line younger patients and hydroxycarbamide is second line.
