polycythaemia

Question 1

definition of polycythaemia

Answer 1

An increase in haemoglobin (Hb) concentration above the upper limit of normal for a person’s age and sex.

it is a myeloproliferative disorder - caused by clonal proliferation of myeloid stem cells, which can differentiate into RBCs = excess

Question 2

classification of polycythaemia

Answer 2

relative polycythaemia (normal red cell mass but reduced plasma volume)

absolute (true) polycythaemia (increased red cell mass).

Question 3

aetiology of polycythemia rubra vera

Answer 3

Characterized by malignant clonal proliferation of myeloid cells with variable morphologic maturity and haematopoietic efficiency.

Mutations in JAK2 tyrosine kinase participates in the pathogenesis.

teh erythroid progenitor offspring are unusual - dont need erythropoeitin to avoid apoptosis

Excess proliferation of RBCs, WBCs, and platelets = hyperviscosity and thrombosis

more common if >60yrs

Question 4

aetiology of secondary polycythaemia

Answer 4

appropriate increase in erythropoietin - from chronic hypoxia eg

• chronic lung disease = upregulation of erythrogeneis
• high altitude
• cyanotic congenital heart disease
• heavy smoking

inappropriate rise in erythropoietin

• renal - carcinoma, cysts, hydronephrosis
• hepatocellular carcinoma
• fibroids
• cerebellar haemangioblastoma
• erythropoietin abuse in atheletes

Question 5

aetiology of relative polycythaemia

Answer 5

dehydration eg diuretics, burns, enteropathy

gaisbock’s syndrome - young male smokers with high vasomotor tone and hypertension

obesity, HTN, high alcohol and tabacco intake

Question 6

epidemiology of polycythaemia

Answer 6

Annual UK incidence of polycythaemia rubra vera is 1.5 in 100,000.

45-60yrs

Question 7

sx of polycythaemia

Answer 7

headaches

dyspnoea

tiniitus

blurred vision from hyperviscosity

pruritus after hot bath

night sweats

thrombosis - DVT, stroke

pain from peptic ulcer disease

angina

gout

choreiform movements

Question 8

signs of polycythaemia

Answer 8

plethoric complexion

scratch marks from itching, conjunctival suffusion and retinal venous engorgement

hypertension

splenomegaly - present in 75% of polycythaemia rubra vera

signs of underlying aetiology in secondary causes

Question 9

Ix for polycythaemia

Answer 9

FBC

• high HB (>16.5 g/dL in, female >18.5 g/dL in male)
• high haematocrit (>48%in female >52% in male ),
• low MCV.

isotope dilution techniques

• Using infusion of radiolabelled albumin (131I) and RBCs (51Cr) allow confirmation of plasma volume and red cell mass (RCM) and distinguish between relative and absolute polycythaemia.
• tests are rarely necessary as almost all female patients with Hb>16.5 g/dL and all male patients with Hb>18.5 g/dL have been shown to have high RCM.

Question 10

Ix results for polycythaemia vera

Answer 10

high RCC, high Hb, high HCT, high PCV

high WCC

high platelets

high B12

low serum erythropoietin

JAK2 mutation - present in almost all, not specific to poly vera

bone marrow trephone and biopsy shows erythroid hyperplasia and increased megakaryocytes, hypercellularity

cytogenics to differentiate from CML

raised cell mass ion 51Cr studies and splenomegaly with normal PaO2 is diagnostic

Question 11

ix results for secondary polycythaemia

Answer 11

increased serum erythropoietin

exclude chronic lung disease/hypoxia - pulse oximetry, ABG, CXR

look for erythropoietin-secreting tumours eg abdo CT, brain MRI

Question 12

presentation of polycythaemia vera

Answer 12

may be asymptomatic and detected on FBC

vague sx due to hyperviscocity:

• headache
• dizziness
• tinnitus
• visual disturbance

itching after hot bath and erythromelagia (burning sensation in fingers and toes) - both characteristic

Question 13

signs of polycythaemia vera

Answer 13

facial plethora

splenomegaly

gout possibly - high urate from RBC turnover

features of arterial (cardiac, cerebral, peripheral) or venous (DVT, cerebral, hepatic) thrombosis