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eMCD - Hae > Haematology 3 (Anaemia + Polycythaemia) > Flashcards

Haematology 3 (Anaemia + Polycythaemia) Flashcards

1
Q

What is anaemia?

A

Anaemia = reduction in amount of hb in a given volume of blood - below what would be expect of a healthy subject

I.e hb is reduced
- rbc and hct usually also reduced

  • usually due to reduction in hb
  • but sometimes due to increase in volume of plasma (this type of anemia doesn’t persist in healthy individuals - excreted)
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2
Q

What is the mechanism of anaemia ?

A
  • reduced rbc / hb production in bone marrow
  • loss of blood from the body
  • reduced survival of rbc in circulation
  • pooling of rbc in enlarged spleen
  • note: mechanism = e.g reduced synthesis of hb
    Cause = e.g condition causing reduced synthesis of haem or globin
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3
Q

What are the classification if anaemia based on cell size?

A
  • Microcytic (HYPOchromic)
  • Normocytic (NORMOchromic)
  • Macrocytic (NORMOchromic)
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4
Q

What are the common causes of microcytic anaemia ?

A

Common causes of microcytic anaemia

a) defect in haem synthesis
- iron deficiency
- anaemia of chronic disease

b) defect in globin synthesis (thalassaemia)
- defect in alpha chain synthesis (alpha thalassaemia)
- defect in beta chain synthesis (beta thalassaemia)

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5
Q

What is macrocytic anaemia?

And what is the most common cause of macrocytic anaemia?

A

Macrocytic anaemia = average cell size is increased

  • usually results from abnormal haemopoiesis (rbc precursors continue to synthesise hb + other cellular proteins but fails to divide normally —> so rbc end up being much larger than normal)

Cause:
1. megaloblastic erythropoiesis (delay in maturation of nucleus while cytoplasm continues to mature + the cell continues to grow)

  1. premature release of cells from the bone –> raises the mean cell volume
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6
Q

What is a feature of a megaloblast?

What is an alternative mechanism of macrocytosis?

A

Megaloblast :

  • larger than normal
  • shows nuclei-cytoplasmic dissociation
  • nuclear development is not matching cytoplasmic development

Macrocytosis alternative mechanisms:
- premature release of cells from the bone marrow
(Reticulocytes -young rbc are 20% larger than mature rbc so increase in proportion = increase in MCV)

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7
Q

State various causes of macrocytosis

A
  • lack of vit b12 or folic acid
  • use of drugs interfering with dna synthesis
  • liver disease and ethanol toxicity
  • recent major blood loss (reticulocytes increased)
  • haemolytic anaemia (reticulocytes increased)
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8
Q

What is the mechanism behind normocytic normochromic anaemia ?

A
  • recent blood loss
  • failure of production of rbc
  • pooling of rbc in the spleen
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9
Q

What are the causes of normocytic normochromic anaemia ?

A
  • peptic ulcer
  • oesophageal varies
  • trauma
  • failure of production of rbc
    (e. g early stages of iron deficiency , renal failure, bone marrow failure, bone marrow infiltration)
  • hypersplenism e.g portal cirrhosis
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10
Q

What is haemolytic anaemia ?

A

Haemolytic anaemia = anaemia resulting from shortened survival of rbc in the circulation

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11
Q

How might haemolysis occur?

A

Haemolysis can result from:

a) intrinsic abnormality of rbc
b) extrinsic factors acting on normal rbc

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12
Q

How is haemolytic anaemia classified?

A

a) intravascular haemolysis
- occurs if there is very acute damage to the rbc

b) extravscular haemolysis
- occurs when defective rbc are removed by the spleen

(Often haemolysis = partly both intra+extravascular)

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13
Q

When would you suspect haemolytic anaemia?

A
  • unexplained anaemia which is normochromic and usually either normocytic / macrocytic
  • evidence of morphologically abnormal rbc
  • evidence of increase rbc breakdown
  • evidence of increased bone marrow activity
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14
Q

What is hereditary spherocytosis ?

A

Hereditary spherocytosis:
- haemolytic anaemia or chronic compensates haemolysis due to inherited intrinsic defect of rbc memb

  • when they enter circulation, the cells lose memb in the spleen and becomes spherocytic
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15
Q

What are the features of hereditary spherocytosis ?

And what is the consequence of it?

A

Features:

  • cells are larger + rounder
  • increased MCHC
  • rbc becomes less flexible (they are removed prematurely in the spleen - extravascular haemolysis )

Consequence:

  • bone marrow responds to haemolysis by increasing rbc output —> leads to polychromasia + reticulocytosis
  • haemolysis leads to increased bilirubin production (jaundice + gallstones)
  • spherocytes can move through gaps so you get early removal of these cells in the spleen
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16
Q

What is the only effective treatment for hereditary spherocytosis?

A

Splenectomy

Good diet / folic acid tablet may also help
- patients with haemolysis = quickly becomes folate deficient

17
Q

Why is glucose-6-phosphate dehydrogenase deficiency important?

A

G6PD:

  • important enzyme involved in pentose phosphate pathway
  • G6PD = only source of reduced glutathione rbc
  • essential for protection of rbc from oxidant damage
18
Q

What happens if a patient has glucose - 6 - phosphate dehydrogenase deficiency?
What happens to the appearance of cells?

A
  • they are at risk if haemolytic anaemia in states of oxidative stress
  • causes intermittent, severe intravascular haemolysis following infection or exposure to an exogenous oxidant.
  • episodes of intravascular hemolysis

Appearance:

  • associated with presence of irregularly contracted cells
  • hb is denatured (forms Heinz bodies)
19
Q

How does acute haemolytic anaemia occur?

A

Acute haemolytic anaemia occurs due to:

  • production of antibodies against red cell antigens
  • immunoglobulin bound to rbc memb = recognised by splenic macrophages
  • which removes parts of the cell memb —> spherocytosis
20
Q

What is the consequence / effects of autoimmune haemolytic anaemia?

A
  • Anaemia
  • spherocytosis

Effects:

  • due to spherocytosis =
  • cell rigidity + recognition of antibody and complement on red cell surface by splenic macrophages —> removal of cells from circulation (by spleen)
21
Q

How would you diagnose autoimmune haemolytic anaemia?

A
  • find spherocytes + increased reticulocyte count
  • detect immunoglobulin on rbc surface
  • detect antibodies to rbc antigens / or other antibodies in the plasma
22
Q

How would you treat autoimmune haemolytic anaemia?

A
  • corticosteroids + other immunosuppressive agents

- splenectomy for severe cases

23
Q

what happens in megaloblastic erythropoiesis?

A

(delay in maturation of nucleus while cytoplasm continues to mature + the cell continues to grow)

24
Q

common causes of macrocytic anaemia

A
  • lack of vit b12 / folic acid
  • use of drugs interfering with DNA synthesis
  • liver disease + ethanol toxicity
  • recent major blood loss (increase in reticulocytes)
  • hemolytic anaemia
25
Q

How is the cause of haemolytic anaemia classified?

A

a) inherited haemolytic anaemia
- can result from abnormalities of the cell memb / hb / enzymes
- defect in glycolytic pathway
- defect in enzyme of pentose shunt

b) acquired haemolytic anaemia
- usually results from extrinsic factors (e.g microorganisms, chemicals or drugs that damage rbc. e.g snake bite )
- dameg to whole red cell
- oxidant exposure –> causing damage to rbc cell memb/hb –> precipitation of episodic haemolysis individiual deficient of enzymes

26
Q

signs pf haemolytic anaemia in children

A
  • pigement stones -> gall stones in children

- jaundiced

27
Q

give examples of inhertied/ acquired HA

A

inherited:
- spherocytosis

acquired:
- autoimmune hemolytic anaemia
- macroangiopathic HA

28
Q

how does spherocytosis cause extravascular hemolysis

A
  • spherocytosis
  • -> less flexible + are removed prematurely by the spleen –> extravascular hemolysis
  • -> can cause jaundice at young age
29
Q

how would you treat microangiopathic haemolytic anaemia?

A
  • remove cause e.g treat severe hypertension / stop causative drug
  • plasma exchange
30
Q

patient with polycythaemia = sees urine in blood
most likely due to

  • chronic renal failure
  • living at high altitude
  • hypoxia from COPD
  • hemolysis
  • renal carcinoma
A
  • renal carcinoma
31
Q

What is megaloblastic anaemia?

A

• Low blood Hb in a given volume due to nuclear-cytoplasmic dissociation of RBC maturation

32
Q

What might you seen in a peripheral blood film of megaloblastic anaemia?

A
  • Hyper segmented neutrophils
  • Giant metamyelocytes
  • Anisocytosis and Poiklocytosis

eMCD - Hae (11 decks)

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