Topic 6.1 - Haemolytic Anaemia: Intracorpuscular Defects 1

Question 1

Define haemolytic anaemia.

Answer 1

Haemolytic anaemia is defined as anaemia resulting from an increase in the rate of red blood cell destruction.

Question 2

What are the 2 fundamental defects causing cause premature destruction of RBC?

Answer 2

1. Intracorpuscular (fault lies in the cell)

2. Extracorpuscular (fault lies in patients plasma or tissues)

Question 3

Give more examples of intracorpuscular defects.

clue: 2 main categories

Answer 3

• can be hereditary or acquired
  (a) hereditary
• defects in RBC membrane
• enzyme deficiency
• haemoglobinopathies
• thalassemia
  (b) Acquired
• paroxysmal nocturnal haemoglobinuria

Question 4

Give 7 examples of extracorpuscular defects.

Answer 4

• immune hemolytic anaemia
• infection
• chemical/toxins
• physical agent
• micro/macroangiopathic hemolytic anaemia
• splenic sequestration (hypersplenism)
• general systemic disorders whereby hemolysis is not the dominant feature of the anaemia

Question 5

What is haemolysis characterised by?

Answer 5

1. Increased RBC destruction in peripheral blood

2. increased RBC production in bone marrow

Question 6

What are 6 tests that reflect increased RBC destruction and what will their results be?

Answer 6

• Serum unconjugated bilirubin (increased)
• Serum haptoglobin (decreased)
• Increased haemoglobin in blood??
• Haemoglobinuria (present)
• Haemosiderinuria (present)
• Methemalbumin, Schumm’s test (positive)

Question 7

What are the tests reflecting increased RBC production?

Answer 7

• compensatory bone marrow response to haemolysis means increased reticulocyte count

RPI (reticulocyte production index) should be calculated: percentage reticulocyte divided by maturation time, multiplied by HCT over 45. If the haemolytic state, RPI > 2.5 to 3.0

Maturation time
45% Hct - 1 day
35% Hct - 1.5 days
25% Hct - 2 days
15% Hct - 2.5 days

Question 8

What are the 4 classifications of the defects of the RBC membrane

Answer 8

1. Hereditary spherocytosis (HS)
2. Hereditary elliptocytosis (HE)
3. Hereditary stomatocytosis
4. Hereditary xerocytosis

Question 9

What is Hereditary Spherocytosis and what is the pathophysiology?

Answer 9

• autosomal recessive inheritance
• most common hereditary haemolytic anaemia in northern Europeans

Pathophysiology:

• fundamental expression of the defect is a loss of surface area of the red cell, decreasing surface to volume ratio -> spherocytosis
• defects of RBC membrane proteins

Question 10

What are the clinical findings for HS?

Answer 10

1. Evidence of haemolytic process
2. RBC indices
3. PBF morphology
4. Special test: osmotic fragility, autohemolysis
5. RBC studies