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Haematology > Haemoglobinopathies > Flashcards

Haemoglobinopathies Flashcards

1
Q

What is a haemoglobinopathy?

A

Conditions affecting globin chains

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2
Q

How do you diagnose a haemoglobinopathy?

A

FBC- Hb
Blood film
Ethnic origin
Quantify haemoglobins

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3
Q

How do you quantify haemoglobins?

A

Electrophoresis
High performance liquid chromatography (HPLC)
Raised HbA2 diagnostic of beta thal trait

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4
Q

What are the two categories of haemoglobinopathy?

A

Thalassemias

Structural haemoglobin variants

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5
Q

What is a thalassemia?

A

Low levels of a Hb chain

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6
Q

What are the two forms of thalassemia?

A

Alpha thalassemia

Beta thalassemia

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7
Q

WHat chain is affected in alpha thalassemia?

A

Alpha

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8
Q

What is a risk factor for alpha thalassemia?

A

Asian origin

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9
Q

How many gene copies do we have of alpha Hb gene?

A

4 (2 per chromasome)

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10
Q

What is the genotype of someone without alpha thalassemia?

A

aa/aa

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11
Q

What are the three variants of thalassemia?

A

Thalassemia trait
HbH disease
Hb Barts hydrops fetalis

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12
Q

What is the genotype of thalassemia trait?

A

a-/aa
–/aa
a-/a-

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13
Q

Describe thalassemia trait

A

Asymptomatic carrier.
Microcytic hypochromic RBC w/ mild anaemia
Ferratin normal

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14
Q

What is ferratin like in thalassemia trait?

A

Normal

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15
Q

What are RBC like in thalassemia trait?

A

Microcytic hypochromic RBC w/ mild anaemia

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16
Q

What is the genotype of HbH disease?

A

–/-a

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17
Q

Describe HbH

A

Anaemia with v low MCV and MCH.

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18
Q

What is HbH?

A

Excessive beta chains form tetramers called HbH.

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19
Q

What are the symptoms of HbH disease?

A

Jaundice
Splenomegaly (increased destruction and extramedullary haematopoesis).
Golf ball like cells.
Iron overload.

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20
Q

How do you treat HbH disease?

A

Transfusion if ill.
Splenectomy.
Folic acid.

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21
Q

What is the genotype of Hb Barts hydrops fetali?

A

–/–

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22
Q

What are the symptoms of Hb Barts hydrops fetali?

A 
Profound anaemia
Cardiac failure
Growth retardation
Severe hepatosplenomegaly
Skeletal and cardiovascular abnormalities
Almost all die in utero
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23
Q

What Hb do you get in Hb Barts hydrops fetali?

A

Get gamma (Bart’s) and beta tetramers.

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24
Q

What chain is affected in beta thalassemia?

A

Beta

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25
Q

What causes beta thalassemia?

A

Autosomal recessive point mutations

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26
Q

How is alpha thalassemia inherited?

A

Autosomal recessive

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27
Q

What are three variants of beta thalassemia?

A

Beta thalassemia trait
Beta thalassemia intermedia
Beta thalassemia major

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28
Q

What are the three gene forms of beta Hb gene?

A

B Normal
B+ Reduced activity
B0 No beta

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29
Q

How does beta thalassemia affect HbA?

A

Excess

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30
Q

WHat does the excess HbA in beta thalassemia cause?

A

Haemolysis

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31
Q

What is the genotype of beta thalassemia trait?

A

B/B+

B/B0

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32
Q

What are the symptoms of beta thalassemia trait?

A

Asymptomatic

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33
Q

Describe beta thalassemia trait

A

Microcytosis w or w/o mild anaemia

Similar to iron deficient anaemia (low MCV/MCH) but normal transferrin and serum ferritin.

34
Q

How do you diagnose beta thalassemia trait

A

Raised HbA2

35
Q

What is the genotype of beta thalassemia intermedia?

A

B+/B+

B+/B0

36
Q

How do you treat beta thalassemia intermedia?

A

Occasional blood transfusions

37
Q

What are some symptoms of beta thalassemia intermedia?

A 
Jaundice
Splenomegaly
Bone deformities
Recurrent leg ulcers
Gallstones 
Infections.
38
Q

What is a complication of beta thalassemia intermedia?

A

Iron overloaded due to increased absorption.

39
Q

What is the genotype of beta thalassemia major?

40
Q

What is the goal of treating beta thalassemia major?

A

Aim it to suppress ineffective erythropoesis and prevent bony deformities.

41
Q

How do you treat beta thalassemia major?

A

Regular blood transfusion
Splenectomy- After 6YO if need too many transfusions
Bone marrow transplant

42
Q

Who should you test for beta thalassemia major?

A

Partner to check of ability to pass on

43
Q

What organs can regular blood transfusions damage?

A

Endocrine
Liver
Heart
Pancreas

44
Q

What are some symptoms of beta thalassemia major?

A

Pallor
Failure to thrive.
Extramedullary heamatopoesis causes: hepatosplenomegaly, skeletal changes (SC compression, skull expansion- frontal bossing, ‘hair on end’ skull XR) and organ damage.

45
Q

How do blood cells present in beta thalassemia major?

A

Target cells

Abnormal size/shape RBC seen on film.

46
Q

When does beta thalassemia major present?

47
Q

What Hb replaces HbA in beta thalassemia major?

48
Q

What are some side effects of iron overload?

A 
Endocrine dysfunction (diabetes, osteoporosis) 
Cardiac disease (cardiomyopathy, arrhythmias)
Liver disease (cirrhosis, cancer)
49
Q

How do you treat iron overload?

A

Iron chelating agents (desferioxamine)

50
Q

What should you do is a patient with beta thalassemia major needs too many transfusions?

A

Splenectomy- need to wait until after 6YO

51
Q

WHat should you give to a patient with a splenectomy?

A

Prophylaxis fro infection (vaccination and penicillin.

52
Q

What is an alternative to a splenectomy?

A

Bone marrow transplant

53
Q

How do you diagnose beta thalassemia major?

A

Check Hb types- No HbA but HbF

Pb levels

54
Q

What is a differential for beta thalassemia major?

A

Pb poisoning

55
Q

What are some consequences of thalassemias?

A

Microcytic anaemia
Toxic accumulation of globin in cell
Haemolysis
Ineffective erythropoiesis

56
Q

What are Hb levels like in conditions of structural haemoglobin variants?

A

Normal Hb levels but mutated Hb

57
Q

What Hb variant is seen in structural haemoglobin variants?

58
Q

What disorders are a major category of structural haemoglobin variants?

A

Sickling disorders

59
Q

What are the variants of sickling disorders?

A

Sickle cell trait
Sickle cell anaemia
Sickle cell disease

60
Q

What is the genotype of sickle cell trait?

A

HbAS

One normal beta gene and one HbS gene. HbS <50%

61
Q

What are the symptoms of sickle cell trait?

A

Asymptomatic carrier- HbS levels too low to polymerise. Only show symptoms under severe oxygen stress (high altitude).

62
Q

What is a benefit of sickle cell trait?

A

Gives some protection from malaria- balanced polymorphism.

63
Q

How does sickle cell blood show on film?

64
Q

How do you diagnose sickle cell trait?

A

Sickle cell test or Hb electrophoresis.

65
Q

What is the genotype of sickle cell anaemia?

A

HbSS
Two mutated beta chains
HbS > 80%

66
Q

What are the pathophysiologies of sickle cell anaemia?

A 
Chronic haemolysis (shortened RBC life span). 
Sickle cells get sequestered into spleen which shrinks (hyposplenism) due to repeated infarcts.
67
Q

What are some complications of sickle cell anaemia?

A

Osteomyelitis- S. Aureus, Staph, Salmonella
Splenic sequestration
Bone marrow aplasia
Leg ulcers
Cardiac problems- Cardiomegaly, arrhythmias
Sickle cell crisis

68
Q

What is splenic sequestration?

A

Acute painful enlargement of spleen.
Pooling of RBC in spleen leading to hypovolemia and death.
Occurs in childhood.
Can occur in liver too.

69
Q

What is bone marrow aplasia?

A

Following erythrovirus B19 infection- invades erythroprogenitor cells.
Rapid fall in Hb with no reticulocytes.

70
Q

What is sickle cell crisis?

A

Episode of tissue infarct due to vascular occlusion- usually in small vessels (hands/feet etc), bones.

71
Q

What are the symptoms of a sickle cell crisis?

A

Extreme pain due to ischemia and inflammation.

Often accompanied by fever.

72
Q

What can precipitate a sickle cell crisis?

A 
Hypoxia
Dehydration
Infection
Cold exposure 
Stress/fatigue
73
Q

What can a sickle cell crisis cause?

A

Hyposplenism and avascular necrosis.

74
Q

What is immediate treatment of a sickle cell crisis?

A 
Opioid analgesia
Hydration
Rest
O2
AntiB if infected
Red cell exchange transfusion in severe crisis eg (lung) chest crisis or (brain)stroke (drain blood and replace)
75
Q

What long term treatment can be used for a sickle cell crisis?

A

Prophylactic penicillin- due to hyposplenism
Vaccination: Pneumococcus, Meningococcus, Haemophilus
Folic acid supplements- Increased RBC turnover
Hydroxycarbamide- Induce HbF production therefore lessening severity.
Regular transfusion- To prevent stroke

76
Q

How do you diagnose sickle cell anaemia?

A

Mix HbS in sodium dithionite- turns turbid. HbA goes clear.
Blood screen- See sickle cells
Sickle solubility test
Hb electrophoresis- Diagnostic

77
Q

How do you manage sickle cell anaemia?

A

Avoid precipitants
Blood transfusion if critical/unstable
LDHLDHamide (hydroxyurea)- Increased HbF
Bone marrow transplant

78
Q

What is sickle cells disease?

A

HbS and other beta chain mutation- eg. HbS and thalassaemia.

79
Q

How does HbS form?

A

Point mutation alters beta chain to HbS

80
Q

How is HbS pathogenic?

A

HbS polymerises if exposed to low O2, infection, cold, dehydration or acidosis.
Forms rods and distorts the RBC which becomes rigid and sickled- initially reversible but with repeats becomes irreversible.
Impairs RBC life and movement through microcirculation (can result in infarct)

81
Q

Why does HbS often go unnoticed?

A

Release O2 more easily therefore don’t notice anaemia normally (until crisis).

Haematology (12 decks)

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