ANSWER 56
This patient has polycythaemia rubra vera. This is due to abnormal proliferation of red
cell precursors derived from a single haematopoietic progenitor cell with the capacity for
differentiation down red cell, white cell and platelet lines. As a result, there is an increase
in haemoglobin, white cell count and platelet level. Patients may present with a throm-
botic event or with symptoms due to increased blood viscosity such as headaches, tinni-
tus and blurred vision. There is an increased bleeding tendency. Splenomegaly is common.
Severe pruritus is characteristic and is particularly related to warmth occurring on getting
into a warm bed or bath.
- Obstructive jaundice due to bile salt retention
- Iron deficiency
- Lymphoma
- Carcinoma, especially bronchial
- Chronic renal failure, partially due to phosphate retention
! Conditions associated with generalized pruritus without a rash
This patient should be referred to a haematology unit for investigation. It is important to
exclude relative polycythaemia due to dehydration from diuretic and alcohol use. The red
cell mass will be raised in polcythaemia rubra vera, but normal in relative polycythaemia.
The following causes of secondary polycythaemia must be excluded:
- chronic lung disease with hypoxia
- cyanotic congenital heart disease
- renal cysts, tumours, renal transplants
- hepatoma, cerebellar haemangioblastoma, uterine fibroids
- Cushing’s disease.
The erythropoietin level is low in polycythaemia rubra vera and high in secondary poly-
cythaemia. Pulse oximetry or arterial blood gases should be performed to exclude hypoxia.
The leucocyte alkaline phosphatase level is also raised in polycythaemia rubra vera.
The patient should be venesected until the haematocrit is within the normal range. A var-
iety of agents can be used to keep the haematocrit down:^32 P, hydroxyurea and busulphan.
The disease may transform into acute leukaemia or myelosclerosis.
- Severe generalized pruritus is a characteristic symptom of polycythaemia rubra vera.