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TAS Haematology > Red Cell Enzyme Defects ✅ > Flashcards

Red Cell Enzyme Defects ✅ Flashcards

1
Q

What is the most common red cell enzyme deficiency causing haemolytic anaemia?

A

Glucose-6-phosphate dehydrogenase (G6PD)

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2
Q

What does G6PD protect against?

A

Protects the cell from oxidative damage

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3
Q

What does G6PD do?

A

Catalyses the first step of the pentose phosphate pathway, regulating the rate of the pathway

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4
Q

What is the inheritance of G6PD deficiency?

A

X-linked

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5
Q

What is the result of G6PD deficiency being a X-linked disorder?

A

It predominantly affects boys, although female carriers may be mildly affected

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6
Q

Who is G6PD deficiency most prevalent in?

A

Patients of African, Mediterranean, or Asian origin

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7
Q

Are patients with G6PD deficiency always symptomatic?

A

No, majority of patients are asymptomatic most of the time, although some rare mutations can cause chronic haemolytic anaemia

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8
Q

What is one of the most common presentations of G6PD deficiency?

A

Neonatal jaundice

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9
Q

Is the neonatal jaundice caused by G6PD deficiency severe?

A

Potentially, can be severe enough to cause kernicterus

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10
Q

What is thought to be the cause of the jaundice in G6PD deficiency?

A

Liver dysfunction, rather than haemolysis

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11
Q

What blood results support the theory that the jaundice in G6PD deficiency is predominantly due to liver dysfunction rather than haemolysis?

A

Despite marked hyperbilirubinaemia, the Hb is usually normal or very slightly reduced

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12
Q

How does G6PD deficiency present after the neonatal period?

A

Usually as an acute haemolytic crisis

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13
Q

What can precipitate an acute haemolytic crisis in G6PD deficiency?

A
  • Infection
  • Certain drugs
  • Ingesting broad beans
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14
Q

What will blood tests during an acute haemolytic crisis due to G6PD deficiency show?

A
  • Reduced Hb
  • Raised reticulocytes
  • Hyperbilirubinaemia
  • Increased LDH
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15
Q

What will be showed on blood film in acute haemolysis caused by G6PD deficiency?

A
  • Fragmented red cells
  • ‘Bite’ cells
  • Polychromasia
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16
Q

What can be seen on blood film in acute haemolysis caused by G6PD deficiency if special stains are used?

A

Heinz bodies

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17
Q

What are Heinz bodies?

A

Red cell inclusions made up of denatured Hb

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18
Q

What does the blood film show in G6PD deficiency between haemolytic crises?

A

Completely normal

19
Q

Is the reticulocyte count increased in G6PD deficiency between haemolytic crises?

A

No

20
Q

What is the treatment for G6PD deficiency?

A

Treatment is unnecessary apart from during severe haemolytic episodes, were red cell transfusion may be required

21
Q

How is diagnosis confirmed in G6DPD deficiency?

A

By measuring red cell G6PD levels

22
Q

When might red cell G6PD levels be falsely elevated?

A

During an acute crisis

23
Q

What advice should be given after a diagnosis of G6PD deficiency?

A

Parents and children should be advised about avoiding potential triggers, and given a list of the most commonly used drugs which may precipitate acute haemolysis

24
Q

How common is pyruvate kinase deficiency compared to G6PD deficiency?

A

Much less common

25
Q

When should pyruvate kinase deficiency be considered?

A

In presence of family history, or after excluding G6PD deficiency

26
Q

What does a deficiency of pyruvate kinase in RBCs result in?

A

Insufficient ATP production, leading to ‘rigid’ cells and subsequent haemolysis

27
Q

How might pyruvate kinase deficiency present?

A
  • Hydrops fetalis
  • Neonatal haemolytic anaemia
  • Chronic haemolytic anaemia in early childhood
28
Q

Is the level of anaemia variable in pyruvate kinase deficiency?

A

Yes

29
Q

Why is the anaemia surprisingly well tolerated in pyruvate kinase deficiency?

A

Because increased 2,3-DPG levels shift the O2 dissociation curve to the right

30
Q

What can be required in severe causes of pyruvate kinase deficiency?

A

Patients can be transfusion dependent

31
Q

What is the inheritance pattern of pyruvate kinase deficiency?

A

Autosomal recessive

32
Q

What is found on the blood film in pyruvate kinase deficiency?

A

‘Prickle’ red cells

33
Q

How can a diagnosis of pyruvate kinase deficiency be made?

A

Measuring pyruvate kinase enzyme levels

Usually necessary to test affected child and their parents to confirm the diagnosis

34
Q

What happens in autoimmune haemolytic anaemia (AIHA)?

A

An antibody against a persons own red cells is produced

35
Q

What can AIHA be divided into?

A

Warm and cold types

36
Q

What is the difference between warm and cold AIHA?

A

In warm, antibody binds most strongly at 37 degrees

In cold, binds most strongly at 4 degrees

37
Q

What antibody is usually involved in warm AIHA?

A

IgG

38
Q

What antibody is usually involved in cold AIHA?

A

IgM

39
Q

When does AIHA most commonly present in children?

A

During intercurrent infection

40
Q

What normally happens when AIHA occurs during intercurrent infection?

A

It resolves spontaneously

41
Q

What might AIHA occur in association with?

A
  • Another immunological disorder, such as SLE or juvenile idiopathic arthritis (JIA)
  • Lymphoproliferative disorder, such as Hodgkin’s lymphoma
42
Q

How is a diagnosis of AIHA confirmed?

A
  • Characteristic blood film
  • Haemolysis profile
  • Positive DAT
43
Q

What is a haemolysis profile?

A
  • Unconjugated hyperbilirubinaemia
  • Raised LDH
  • Increased reticulocytes
  • Reduced haptoglobin levels
44
Q

What might be required in causes of AIHA that do not resolve spontaneously?

A

Immunosuppressive treatment, such as steroids, azathioprine, or cyclosporin

TAS Haematology (7 decks)

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