Page 319 - Concise Pathology for Exam Preparation ( PDFDrive )

304 SECTION II Diseases of Organ Systems

Q. Enumerate the causes of intravascular haemolysis.

Ans. Causes of intravascular haemolysis:
• Microangiopathic haemolytic anaemia (sickle cell anaemia, DIC and TTP)
• Physical injury (mechanical trauma and thermal injury)
• PNH
• G6PD deficiency
• Autoimmune haemolytic anaemia
• Mechanical heart valves
• March haemoglobinuria (seen in vigorous exercise)
• Pregnancy-induced hypertension
• Infections—P. falciparum and Clostridium perfringens
• Disseminated malignancy
• Haemolytic uraemic syndrome.

Q. Enumerate the causes of extravascular haemolysis.

Ans. Causes of extravascular haemolysis:
• All red cell membrane defects, eg, hereditary spherocytosis
• Sickle cell anaemia
• Premature destruction of RBCs, eg, thalassaemia or other Hb synthesis disorders
• Splenomegaly (hypersplenism)

Q. Enumerate the steps in the laboratory diagnosis of haemolytic
anaemia.
Ans. There are three main components of haemolytic anaemia:
1. Premature destruction of red cells
2. Accumulation of products of haemoglobin breakdown
3. Accelerated erythropoiesis in bone marrow

Laboratory Evidence of Increased RBC Breakdown
• Increased serum bilirubin (mainly unconjugated)
• Increased faecal stercobilinogen
• Increased urinary urobilinogen
• Increased plasma LDH (LDH2 . LDH1)

Laboratory Evidence of Intravascular Haemolysis
• Decreased or absent serum haptoglobin and haemopexin (haemoglobin-binding
proteins)
• Haemoglobinaemia, haemoglobinuria and methaemalbuminaemia
• Haemosiderinuria
• Jaundice

Laboratory Evidence of Compensatory Erythroid Hyperplasia
• Increased reticulocyte count
• Macrocytosis, polychromasia and stippling
• Erythroid hyperplasia

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