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Haemoglobinopathies Flashcards

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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
What causes beta thalassemia?
Autosomal recessive point mutations
26
How is alpha thalassemia inherited?
Autosomal recessive
27
What are three variants of beta thalassemia?
Beta thalassemia trait Beta thalassemia intermedia Beta thalassemia major
28
What are the three gene forms of beta Hb gene?
B Normal B+ Reduced activity B0 No beta
29
How does beta thalassemia affect HbA?
Excess
30
WHat does the excess HbA in beta thalassemia cause?
Haemolysis
31
What is the genotype of beta thalassemia trait?
B/B+ | B/B0
32
What are the symptoms of beta thalassemia trait?
Asymptomatic
33
Describe beta thalassemia trait
Microcytosis w or w/o mild anaemia | Similar to iron deficient anaemia (low MCV/MCH) but normal transferrin and serum ferritin.
34
How do you diagnose beta thalassemia trait
Raised HbA2
35
What is the genotype of beta thalassemia intermedia?
B+/B+ | B+/B0
36
How do you treat beta thalassemia intermedia?
Occasional blood transfusions
37
What are some symptoms of beta thalassemia intermedia?
``` Jaundice Splenomegaly Bone deformities Recurrent leg ulcers Gallstones Infections. ```
38
What is a complication of beta thalassemia intermedia?
Iron overloaded due to increased absorption.
39
What is the genotype of beta thalassemia major?
B0/B0
40
What is the goal of treating beta thalassemia major?
Aim it to suppress ineffective erythropoesis and prevent bony deformities.
41
How do you treat beta thalassemia major?
Regular blood transfusion Splenectomy- After 6YO if need too many transfusions Bone marrow transplant
42
Who should you test for beta thalassemia major?
Partner to check of ability to pass on
43
What organs can regular blood transfusions damage?
Endocrine Liver Heart Pancreas
44
What are some symptoms of beta thalassemia major?
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
How do blood cells present in beta thalassemia major?
Target cells | Abnormal size/shape RBC seen on film.
46
When does beta thalassemia major present?
6-24m
47
What Hb replaces HbA in beta thalassemia major?
HbF
48
What are some side effects of iron overload?
``` Endocrine dysfunction (diabetes, osteoporosis) Cardiac disease (cardiomyopathy, arrhythmias) Liver disease (cirrhosis, cancer) ```
49
How do you treat iron overload?
Iron chelating agents (desferioxamine)
50
What should you do is a patient with beta thalassemia major needs too many transfusions?
Splenectomy- need to wait until after 6YO
51
WHat should you give to a patient with a splenectomy?
Prophylaxis fro infection (vaccination and penicillin.
52
What is an alternative to a splenectomy?
Bone marrow transplant
53
How do you diagnose beta thalassemia major?
Check Hb types- No HbA but HbF | Pb levels
54
What is a differential for beta thalassemia major?
Pb poisoning
55
What are some consequences of thalassemias?
Microcytic anaemia Toxic accumulation of globin in cell Haemolysis Ineffective erythropoiesis
56
What are Hb levels like in conditions of structural haemoglobin variants?
Normal Hb levels but mutated Hb
57
What Hb variant is seen in structural haemoglobin variants?
HbS
58
What disorders are a major category of structural haemoglobin variants?
Sickling disorders
59
What are the variants of sickling disorders?
Sickle cell trait Sickle cell anaemia Sickle cell disease
60
What is the genotype of sickle cell trait?
HbAS | One normal beta gene and one HbS gene. HbS <50%
61
What are the symptoms of sickle cell trait?
Asymptomatic carrier- HbS levels too low to polymerise. Only show symptoms under severe oxygen stress (high altitude).
62
What is a benefit of sickle cell trait?
Gives some protection from malaria- balanced polymorphism.
63
How does sickle cell blood show on film?
Normal
64
How do you diagnose sickle cell trait?
Sickle cell test or Hb electrophoresis.
65
What is the genotype of sickle cell anaemia?
HbSS Two mutated beta chains HbS > 80%
66
What are the pathophysiologies of sickle cell anaemia?
``` Chronic haemolysis (shortened RBC life span). Sickle cells get sequestered into spleen which shrinks (hyposplenism) due to repeated infarcts. ```
67
What are some complications of sickle cell anaemia?
Osteomyelitis- S. Aureus, Staph, Salmonella Splenic sequestration Bone marrow aplasia Leg ulcers Cardiac problems- Cardiomegaly, arrhythmias Sickle cell crisis
68
What is splenic sequestration?
Acute painful enlargement of spleen. Pooling of RBC in spleen leading to hypovolemia and death. Occurs in childhood. Can occur in liver too.
69
What is bone marrow aplasia?
Following erythrovirus B19 infection- invades erythroprogenitor cells. Rapid fall in Hb with no reticulocytes.
70
What is sickle cell crisis?
Episode of tissue infarct due to vascular occlusion- usually in small vessels (hands/feet etc), bones.
71
What are the symptoms of a sickle cell crisis?
Extreme pain due to ischemia and inflammation. | Often accompanied by fever.
72
What can precipitate a sickle cell crisis?
``` Hypoxia Dehydration Infection Cold exposure Stress/fatigue ```
73
What can a sickle cell crisis cause?
Hyposplenism and avascular necrosis.
74
What is immediate treatment of a sickle cell crisis?
``` 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
What long term treatment can be used for a sickle cell crisis?
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
How do you diagnose sickle cell anaemia?
Mix HbS in sodium dithionite- turns turbid. HbA goes clear. Blood screen- See sickle cells Sickle solubility test Hb electrophoresis- Diagnostic
77
How do you manage sickle cell anaemia?
Avoid precipitants Blood transfusion if critical/unstable LDHLDHamide (hydroxyurea)- Increased HbF Bone marrow transplant
78
What is sickle cells disease?
HbS and other beta chain mutation- eg. HbS and thalassaemia.
79
How does HbS form?
Point mutation alters beta chain to HbS
80
How is HbS pathogenic?
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
Why does HbS often go unnoticed?
Release O2 more easily therefore don't notice anaemia normally (until crisis).

Haematology (12 decks)

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