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Haematology > Haemolytic Anaemias > Flashcards

Haemolytic Anaemias Flashcards

1
Q

What is haemolytic anaemia?

A

Anaemia caused by premature breakdown of RBCs, before their normal life span of approximately 120 days.

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2
Q

How is haemolytic anaemia defined based on where it is occuring?

A
  • Intravascular
  • Extravascular
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3
Q

What system falls under the term extravascular when describing the location that haemolysis is occuring?

A

Reticuloendothelial system - e.g macrophages in the liver, spleen and bone marrow

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4
Q

What are the groups causes of haemolytic anaemia?

A
  • Acquired - immune, non-immune and other causes
  • Hereditary - enzyme or membrane defects, or haemoglobinopathy
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5
Q

What are immune mediated causes of acquired haemolytic anaemia?

A
  • Autoantibodies - Warm, Cold, CHAD, PCH
  • Drug-induced
  • Alloantibodies
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6
Q

What are non-immune causes of of acquired haemolytic anaemia?

A
  • Acquired membrane defects - paroxysmal nocturnal haemoglobinuria
  • Mechanical factors - prosthetic heart valves, or microangiopathic haemolytic anaemia
  • Secondary to systemic disease - renal and liver disease
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7
Q

What are causes of acquired haemolytic anaemia that fall neither under immune or non-immune mediated acquired haemolytic anaemias?

A
  • Toxins
  • Infections
  • Hypersplenism
  • Drugs - oxidative haemolysis
    *
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8
Q

What is a Coomb’s Test?

A

DIRECT ANTIGLOBULIN TEST (DAGT)

A test used to detect the antibodies or complement proteins that are bound to the surface of red blood cells.

A blood sample is taken and the RBCs are washed. These are then incubated with anti-human globulin (“Coombs reagent”). If this produces agglutination of RBCs, the direct Coombs test is positive, a visual indication that antibodies (+/- complement proteins) are bound to the surface of red blood cells.

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9
Q

What are the main types of AIHA?

A
  • Warm Autoantibody
  • Cold Autoantibody

Type is determined depending on whether the antibody attaches better to the red cells at body temperature (37°C) or at lower temperatures

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10
Q

What are causes of Cold autoantibody autoimmune haemolysis?

A
  • Infections - CMV, EBV, chickenpox, measles, mumps, mycoplasma pneumoniae
  • Lymphomas
  • Paroxysmal cold haemoglobinura
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11
Q

What antibody type predominates in Cold autoantibody AIHA?

A

IgM

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12
Q

What are causes of Warm Auto-antibody AIHA?

A
  • Autoimmune rheumatic disorders e.g. SLE
  • CLL
  • Lymphoma’s
  • Carcinoma’s
  • Drugs - metyldopa, penicillins, cephalosporins
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13
Q

What is the predominant type of antibody in warm type AIHA?

A

IgG

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14
Q

If you performed a DAGT and it was positive, what would this indicate?

A

Haemolysis is immune mediated

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15
Q

When performing a DAGT, what would a negative result indicate?

A

Non-immune mediated cause of haemolytic anaemia

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16
Q

If immune haemolysis was present on DAGT, how would you determine what type of autoantibodies are present?

A

Look at temperature at which they bind - Warm/Cold

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17
Q

When taking a history from someone with suspected haemolytic anaemia, what are you looking out for?

A
  • Jaundice
  • Dark urine
  • Previous anaemia
  • Travel
  • Family history
  • Drugs
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18
Q

What might you see on examination in someone with haemolytic anaemia?

A
  • Jaundice
  • Hepatosplenomegaly
  • Gallstones
  • Leg ulcers
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19
Q

If you suspected haemolytic anaemia, what investigations might you do?

A
  • FBC
  • LDH
  • Reticulocyte count
  • Haptoglobin
  • Urinary urobilinogen
  • Bilirubin
  • Thick and thin blood film
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20
Q

How would you approach investigating someone with suspected haemolytic anaemia?

A
  1. Look for increased RBC breakdown - are they haemolysing?
  2. What is the mechanism?
  3. Is it immune mediated or not?
21
Q

What investigaitons would you consider doing when trying to determine if there was red cell breakdown?

A
  • FBC, reticulocyte count, blood film
  • Serum bilirubin (direct/indirect - high)
  • LDH
  • Serum haptoglobin
22
Q

Why is bilirubin unconjugated in haemolytic anaemia?

A

Red cell breakdown is occuring at an increaed rate pre-hepatically

23
Q

Why is LDH increased in haemolytic anaemia?

A

Released from haemolysed RBCs

24
Q

How would you go about trying to determine a mechanism of haemolytic anaemia?

A
  • History and examination
  • Blood film
  • Direct Antiglobulin Test (Coombs’ test)
  • Urine for haemosiderinuria/increased urobilinogen
25
Q

How would you determine if haemolysis was immune mediated or not?

A

Coomb’s Test

26
Q

What is haptoglobin?

A

Protein which mops up free plasma haemoglobin, which is then removed by the liver

27
Q

What is haemosiderinuria?

A

Hemosiderinuria occurs when hemoglobin is released from RBCs into the bloodstream in excess of the binding capacity of haptoglobin.

Excess hemoglobin is filtered by the kidney and reabsorbed in the proximal convoluted tubule, where the iron portion is removed and stored in ferritin or hemosiderin. The tubule cells of the proximal tubule slough off with the hemosiderin and are excreted into the urine, producing a “brownish” color. It is usually seen 3-4 days after the onset of hemolytic condition

28
Q

What features on further blood investigation would indicate intravascular haemolytic anaemia?

A
  • Increased free plasma haemoglobin
  • Decreased plasma haptoglobin
  • Haemoglobinuria
  • Haemosiderinuria
29
Q

What are causes of mechanical haemolytic anaemia?

A
  • Damaged artificial heart valves
  • March haemoglobinuria
  • Microangiopathic haemolytic anaemia (MAHA)
30
Q

If schistocytes were found on blood film, what might this indicate?

A

Microangiopathic haemolytic anaemia

31
Q

What are causes of microangiopathic haemolytic anaemia?

A
  • Malignant hypertension
  • Eclampsia
  • Haemolytic uraemic syndrome
  • Thrombotic thrombocytopenic purpura
  • Vasculitis
  • DIC
32
Q

What re the main groups of hereditary causes of haemolytic anaemia?

A
  • Enzyme defects
  • Membrane defects
  • Haemoglobinopathy
33
Q

What are examples of enzyme deficiencies which lead to haemolytic anaemia?

A
  • G6PD deficiency
  • Pyruvate kinase deficiency
34
Q

What are membrane defects which cause haemolytic anaemia?

A
  • Hereditary spherocytosis
  • Hereditary elliptocytosis
35
Q

What are haemoglobinopathies that cause haemolytic anaemia?

A
  • Thalassemia
  • Sickle Cell Disease
36
Q

What is G6PD deficiency?

A

Glucose-6-phosphate dehydrogenase deficiency

The enzyme G6PD holds a vital position in the hexose monophosphate shunt, oxidizing glucose-6-phosphate to 6-phosphoglycerate with the reduction of NADP to NADPH. The reaction is necessary in red cells where it is the only source of NADPH, which is used via glutathione to protect the red cell from oxidative damage.

Deficiency in this enzyme means that cells are more vulnerable to oxidant damage. After an oxidant shock the Hb level may fall precipitously; death may follow unless the condition is recognized and the patient is transfused urgently.

37
Q

How is G6PD deficiency inherited?

A

X-linked - more common in males

38
Q

What are clinical features of G6PD deficiency?

A

Most are asymptomatic, unless challenged with oxidative stress:

  • Rapid anaemia
  • Neonatal Jaundice
  • Splenomegaly
  • Pigmented gallstones
39
Q

Which individuals are most commonly affected by G6PD deficiency?

A
  • African
  • Mediterranean
  • Middle East
  • Far East
40
Q

What are causes of oxidative crisis in G6PD deficiency?

A
  • Infection
  • Acute illness - DKA
  • Broad Beans
  • Henna Tattoos
  • Drugs - Antimalarials, Sulphonamides and sulpones, Antibacterials, Analgesics, Antihelminthics
41
Q

What would you see on blood film in G6PD defiency?

A

Bite/Bliter cells

42
Q

How would you investigate if you suspected G6PD deficiency?

A

Normal FBC between attacks

  • Enzyme assay
  • Blood film - bite cells during attacks
43
Q

How would you manage someone with G6PD deficiency?

A
  • Avoid Triggers
  • Transfuse if severe
44
Q

What is pyruvate kinase deficiency?

A

This is the most common defect of red cell metabolism after G6PD deficiency. There is reduced production of ATP, causing rigid red cells.

45
Q

How does pyruvate kinase deficiency present?

A
  • Haemolytic anaemia
  • Splenomegaly
46
Q

What would you see on blood film with pyruvate kinase deficiency?

A

Prickle cells

47
Q

What is hereditary spherocytosis?

A

HS is a membrane defect which results in the cells losing part of the cell membrane as they pass through the spleen. The best-characterized defect is a deficiency in the structural protein spectrin. The abnormal membrane in HS is associated functionally with an increased permeability to sodium, and this requires an increased rate of active transport of sodium out of the cells which is dependent on ATP produced by glycolysis.

The surface-to-volume ratio decreases, and the cells become spherocytic. Spherocytes are more rigid and less deformable than normal red cells. They are unable to pass through the splenic microcirculation so they have a shortened lifespan.

48
Q

What is the clinical presentation of hereditary spherocytosis?

A
  • Anaemia
  • Jaundice (neonatal)
  • Splenomegaly
  • Pigment gallstones
49
Q

How would you treat someone with hereditary spherocytosis?

A
  • Folic acid (increased requirements)
  • Transfusion
  • Splenectomy

Haematology (34 decks)

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