Polcythaemia

Question 1

Define Polycythaemia

Answer 1

Increase in haemoglobin concentration above the upper limit normal to age and sex

Relative/pseudo polycythaemia = Reduced plasma volume but RBC mass stays the same

Absolute polycythaemia = Raised RBC mass / total no. of RBC in circulation

Question 2

Aetiology of pseudo-Polycythaemia

Answer 2

Acute: Dehydration

Chronic: Obesity, Hypertension and high alcohol or tobacco intake.

Question 3

Aetiology of absolute Polcythaemia

Answer 3

Primary
- Polycythaemia Vera

Secondary

• Blood Doping or over-transfusion
• Appropriately increased erythropoietin e.g. high altitudes, chronic lung disease, cyanotic congenital heart disease, heavy smoking)
• Inappropriate erythropoietin synthesis or use e.g. renal carcinoma, hepatocellular carcinoma

Question 4

What is polycythaemia vera

Answer 4

myeloproliferative neoplasm (Philadelphia chromosome-negative)

A clonal haematopoietic disorder characterised by erythrocytosis and often thrombocytosis + increased risk of thrombosis and haemorrhage.
Pathogenesis involves JAK2 V617F mutation

Question 5

Symptoms of Polycythaemia

Answer 5

May be asymptomatic

Symptoms due to hyperviscosity:
Headache
Dyspnoea
Tinnitus 
Blurred vision 
Pruritus after hot bath 
Night sweats
Thrombosis symptoms: calf swelling, calf pain, sudden onset SOB, chest pain
Peptic ulcers, angina, gout

Question 6

Signs of Polycythaemia on examination

Answer 6

Plethoric complexion
Scratch marks due to itching
Conjunctival suffusion
Retinal venous engorgement
Hypertension
Splenomegaly (75% of polycythaemia rubra vera)
Signs of underlying aetiology

Question 7

Investigations for polycythaemia

Answer 7

FBC: raised Hb (>16.5) | raised Haematocrit (>48) | MCV reduced | Raised WCC and platelets (rubra vera)
Bone marrow trephine and biopsy: erythroid hyperplasia | raised megakaryocytes]

Isotope dilution techniques: raised cell mass
Serum erythropoietin studies: Reduced serum erythropoietin in polycythaemia vera / Raised serum erythropoietin in secondary polycythaemia
Pulse oximetry, ABG, CXR: exclude pulmonary cause
Abdominal CT/brain MRI: exclude erythropoietin tumours
Cytogenetics: exclude CML
JAK-2 mutation screening: rubra vera +ve