Page 335 - Concise Pathology for Exam Preparation ( PDFDrive )

320 SECTION II Diseases of Organ Systems

2. Absolute: Absolute polycythaemia is associated with an actual increase in the red cell
mass and is of two further types:
(a) Primary (polycythaemia vera): Denotes absolute polycythaemia of unknown
aetiology, which is associated with decreased erythropoietin levels.
(b) Secondary (erythrocytosis): Erythrocytosis secondary to increased production
of erythropoietin as a consequence of hypoxia. It is seen in association with the
following conditions:
(i) High altitude
(ii) Cyanotic congenital heart diseases (TOF—Tetralogy of Fallot and Eisenmenger
complex)
(iii) Pulmonary diseases (eg, COPD)
(iv) Chronic carbon monoxide poisoning and smoking
(v) Abnormal haemoglobin with high oxygen affinity
(vi) Increased production of erythropoietin or erythropoietin-like substance by
tumours and other conditions, as in, cerebellar haemangioblastoma, renal
tumours (carcinoma, adenoma and sarcoma), polycystic kidney disease,
uterine leiomyoma, hepatocellular carcinoma and pheochromocytoma

Q. Outline the clinical features and laboratory diagnosis of
polycythaemia vera.

Ans. Polycythaemia vera is a clonal stem cell disorder characterized by an increased pro-
duction of formed elements of blood by a hyperplastic marrow; however, the disease is
generally dominated by an elevated haemoglobin concentration (haematocrit . 52% in an
adult male and . 48% in an adult female).

Aetiology
Unknown; mutation in JAK2, a tyrosine kinase involved in signalling pathway of the
erythropoietin receptor, is thought to render the erythropoietin receptor hypersensitive
to erythropoietin.

Clinical Features
Seen in middle-aged males who present with dusky red colour of the face (ruddy cyanosis).
Complaints are related to the increased viscosity and stasis of blood and include
• Headache, dizziness, vertigo, visual disturbances, tinnitus and syncope (due to decreased
cerebral perfusion)
• Pruritus (due to histamine release from neoplastic basophils and mast cells)
• Peptic ulceration (due to excessive histamine)
• Splenomegaly and hepatomegaly
• Symptoms of peripheral vascular insufficiency and thrombotic complications usually
affecting the brain and heart; hepatic vein thrombosis resulting in Budd–Chiari syn-
drome (due to stasis)
• Bleeding manifestations like epistaxis, bleeding from peptic ulcer, intramuscular haem-
orrhages and bruising (due to platelet function abnormalities).
• Hyperuricaemia (due to rapid cell turn over) may result in the formation of urate stones
and nephropathy.
Laboratory Diagnosis

• Markedly elevated haemoglobin concentration and haematocrit (Hb is in the range of
18–24 g/dL and PCV ranges between 0.60 and 0.70)
• Increased red cell mass and blood viscosity
• Total white cell count and platelet count are elevated; absolute basophil count is increased.
• The arterial oxygen saturation is normal in contrast to hypoxic erythrocytosis where it
is reduced.
• Bone marrow shows either erythroid hyperplasia or pan hyperplasia.
• Iron stores are depleted.
• Urine and serum levels of erythropoietin are reduced.
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