Polycythaemia

Question 1

what is polycythaemia

Answer 1

increased haemoglobin concentration,

increased haematocrit (PCV) and red cell count

Question 2

what is the difference between relative and absolute polycythaemia

Answer 2

Relative polycythaemia (or pseudo-polycythaemia) is where there is a falsely elevated haemoglobin secondary to a low plasma volume (remember that haemoglobin is measured as a concentration). This can be seen in dehydration or excess diuretic use.

If the plasma volume is normal, the polycythaemia is an absolute polycythaemia (red cell mass will be raised).
Absolute polycythaemia is classified into primary and secondary causes.

Question 3

in relative polycythaemia what will be seen (all results)

Answer 3

increased Hb,

increased PCV (due to decreased plasma levels - can be due to hypovolaemia)

normal red cell count

Question 4

what causes polycythaemia (polycythaemia vera)

Answer 4

Characterised by clonal proliferation of myeloid cells

Question 5

what causes secondary polycythaemia

Answer 5

appropriate increase in EPO -
Due to chronic hypoxia (e.g. chronic lung disease, living at high altitude)

inappropriate increase in EPO-
Renal (carcinoma, cysts, hydronephrosis)
Hepatocellular carcinoma
Fibroids
Cerebellar haemangioblastoma
Secondary polycythaemia may be due to erythropoietin abuse by athletes

Question 6

what causes relative polycythaemia

Answer 6

dehydration and Gaisbocks syndrome

Question 7

what is primary polycythaemia

Answer 7

there is increased erythrocytosis independent of EPO

Question 8

what is Gaisbocks syndrome

Answer 8

prevalent in young male smokers, and is associated with hypertension, which reduces plasma volume, hence resulting in the raised haemoglobin.

Question 9

presenting symptoms of polycythaemia

Answer 9

Fatigue

Headache and Visual disturbances (secondary to hyperviscocity)

Pruritus (typically after a hot bath)

Erythromelalgia (a painful burning sensation in the fingers and toes)

Arterial thrombosis (such as MI or stroke)

Venous thrombosis (such as PE or DVT)

Haemorrhage (intracranial or gastrointestinal)

Paradoxical increased bleeding risk (due to impaired platelet function)

Increased risk of gout (caused by hyperuricaemia secondary to increased cell turnover)

Facial redness on examination

Splenomegaly

Question 10

what will be done investigation wise

Answer 10

bloods - FBC

increased Hb

increased PCV (in absolute polycythaemia)

low MCV