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Inherited Haemoglobin Disorders Flashcards

1
Q

Which chromosomes are associated with the alpha and beta haemoglobin chains?

A 
Alpha= chromosome 16 
Beta= chromosome 11
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2
Q

What are the different types of haemoglobin present in adult blood?

A

HbA (95%)
HbA2 (2.35%)
HbF (0.5-1%)

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3
Q

What is the difference between a qualitative and quantitative haemoglobinopathy? Give an example of a disorder.

A

Qualitative= changes to globin chain amino acid sequence
Eg Sickle cell
Quantitative= complete or partial reduction of chain
Eg Thalassaemia

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4
Q

What is the genetic cause of sickle cell disease?

A

Substitution of glutamic acid at position 6 of beta chain

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5
Q

What is the physiological difference between sickle cell trait and sickle cell disease?

A

Sickle cell trait (HbSs) only has one abnormal beta chain whereas sickle cell disease (HbSS) has 2 abnormal beta chains

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6
Q

Why is sickle cell trait an evolutionary advantage?

A

It provides protection against malaria

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7
Q

When might complications arise with sickle cell trait and what are they?

A

When individual is under physiological stress i.e. pregnancy/illness/sepsis

Consequences:

  • renal disease
  • splenic infarction
  • increased clot risk
  • pregnancy complications
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8
Q

Why do RBC in SCD form sickle shape and what are the consequences of this?

A

HbS polymerises in deoxyhaemoglobin state which alters the RBC structure

Sickle shape means that RBC has decreased deformability leading to veno-occlusion and haemolysis

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9
Q

What type of anaemia is associated with SCD? What are the associated symptoms?

A

Congenital haemolytic anaemia

Jaundice= increased bilirubin production
Pigmented gall stones
Reticulocytosis + folate deficiency secondary to compensatory increase of RBC production

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10
Q

How does sickle cell disease present acutely?

A 
Painful crisis 
Infections i.e. septicaemia/meningitis/UTI/osteomyelitis + encapsulated infections 
Acute chest syndrome 
Stroke
Acute splenic and hepatic sequestration 
Aplastic crisis 
Priapism 
Growth delay
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11
Q

What affect does SCD have on the spleen? What is the clinical consequence of this?

A

Sickled blood cells can lead to sickling in the spleen leading to HYPOSPLENISM and FUNCTIONAL ASPLENIA

Leads to increased risk of encapsulated infection eg Pneumococcus and menigiococcus

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12
Q

What causes haemostatic instability in SCD?

A

Sequestration/pooling of blood in spleen and liver

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13
Q

What is an aplastic crisis?

A

The bone marrow stops the production of blood cells due to SCD

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14
Q

Why does a painful crisis occur in SCD? What are the precipitating factors?

A

Occlusion of small blood vessels due to sickled blood cells lacking deformability

Temperature change
Infection
Stress
Pregnancy

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15
Q

What is the management of SCD painful crisis and what are the possible complications?

A

Analgesia-type dependent on patient
Fluids (oral method preferred)
Oxygen + monitor SATS
LMWH (due to increased risk of thromboembolic events)

Sepsis (not all classic signs might be present making it hard to spot)
Renal (need to monitor fluid balance and renal function)
VTE
Acute sickle chest syndrome

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16
Q

Why is acute sickle chest syndrome associated with SCD?
How would the patient present?
How would you manage a patient presenting with ASCCS?

A

Sickling in lung vasculature leads to respiratory distress

Presentation:
Tachypnoea 
Cough 
Chest and rib pain 
Hypoxia 
Fever 
Radiological evidence of consolidation/pulmonary infiltrates 
Management: (emergency) 
Urgent cross match 
Critical care review 
Respiratory support 
Fluids and physio 
Transfusion i.e. top-up or exchange
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17
Q

What are the implications of SCD as a chronic illness? Give examples.

A

End organ damage

CKD
Chronic sickle lung leading to restrictive lung defect 
Cardiomegaly/RHF/Pulmonary hypertension 
Retinopathy 
Gallstones 
Leg ulcer 
Avascular necrosis of femoral heads 
Erectile dysfunction secondary to priapism
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18
Q

How can SCD be managed chronically?

A

Education and psychological support
Primary and secondary support
Screening i.e. echo for pulmonary hypertension in adults
Manage established conditions

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19
Q

What are specific interventions used in the management of SCD?

A 
Folic acid 
Analgesia 
Infection management:
- penicillin prophylaxis 
- vaccination
-self-referal and empowerment to ask for expertise 
Blood transfusions 
Hydrocarbamide
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20
Q

What are the types of blood transfusion used in SCD management?

A

Top-up
Exchange

Regular transfusion programmes used in children with high risk of trans cranial Doppler to prevent stroke

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21
Q

What is the function of hydroxycarbamide in SCD management?

A

Increases the concentration of HbF and decreases the concentration of HbS

22
Q

What are the risks of blood transfusion?

A 
Alloimmunisation 
Haemolytic transfusion reactions 
Transfusion associated infections 
Iron overload when on chronic tranfusion
Hyperviscosity
23
Q

What causes alpha thalasaemia?

A

-Decreased globan chain production leading to lack of HbA
-Formation of abnormal Hb due to excess of HbB and gamma chains
I.e. HbH (4x beta)= Thal intermedia
Hb Bart’s = not compatible with life

24
Q

What are the consequences of alpha thalassaemia?

A

Ineffective haemopioesis

Haemolysis leading to anaemia

25
What are the 2 types of carrier type for alpha thalassaemia and how does this related to the alpha Hb chains?
High risk: Alpha alpha/ - - I.e. 2 alpha deletions Low risk: Alpha alpha/- alpha I.e. 1 alpha deletion
26
What is the genetic basis for beta thalassaemia and what are the consequences of this?
Decreased or total loss of beta chain production leading to relative excess of alpha chains Excess alpha chains leads to unstable RBC and precipitation of precursors DYSFUNCTIONAL ERYTHROPOIESIS AND HAEMOLYSIS = ANAEMIA
27
What is the difference between beta thalassaemia major and beta thalassaemia intermedia?
Major= homozygous total loss of beta chain production Minor= compound heterzygote I.e. one chain has partial reduction and the other has total loss
28
How would someone with beta thalassaemia present?
Progressive anaemia leading to failure to thrive Cardiac failure Extramedullary haemopoiesis (liver and spleen) Bone over-growth leading to skull and dental abnormalities NOTE: Will likely be detected on antenatal screening
29
What is the main form of treatment/management for beta-thalassaemia? Why is it indicated?
Blood transfusion starting from 6-9 months and continuing 2-4 weekly for life Used to prevent the progressive anaemia caused by the problems associated with decreased beta chains levels
30
What is the major complication associated with chronic blood transfusions? What are the consequences?
Iron overload Growth failure Multiple endocrine dysfunctions Cardiac and hepatic toxicity
31
Why is endocrine dysfunction associated with beta-thalassaemia major?
Iron deposits in the anterior pituitary leads to hypopituitarism which affects the HPA Hypogondism Hypoparathyroidism Hypothyroidism Pancreatic damage
32
How can beta thalassaemia affect the bones and how can this be managed?
Can cause osteoporosis, short stature and bony overgrowth Management: - monitor calcium profile/vit D/PTH to see if they need replacing - monitor bone density - provide sex hormone replacement - life style intervention i.e. smoking/diet/alcohol/exercise
33
Why are cardiac and liver disease associated with beta thalassaemia?
Iron overload can lead to severe cardiac failure, dysrhythmia and liver cirrhosis and increased risk of HCC
34
How is iron overload treated? What are the different methods?
Iron chelation using DESFERRIOXAMINE Subcutaneous infusion 3-5 nights a week overnight starting at 2 yo Oral forms: DEFERASIROX= once daily (Need to monitor renal and liver toxicity) DEFERIPRONE= thrice daily (v effective at removing cardiac iron)
35
How would beta thalassaemia present acutely?
Infections i.e. biliary tract sepsis/unusual sepsis/line-related sepsis Cardiac i.e. dysarythmias + cardiac failure Endocrine i.e. diabetes + hypoadrenal + hypocalcaemia
36
If someone with beta thalassaemia presents with an infection, what is it important to ask them about?
Whether they are on deferiprone i.e. can cause neutropenia which may be the underlying cause of their infection
37
How can beta thalassaemia be cured? What are the associated risks? When is the ideal time for this to be done?
Bone marrow transplant ``` Risks: Death Graft GvHD Infertility ``` 2-3 yo i.e. before associated co-morbidities develop
38
How can you screen for haemoglobinopathies?
Antenatal screening in 1st trimester Neonatal screening i.e. identify neonates with SCD to enable early intervention Sickle solubility test= screens for HbS so will be positive for trait and disease HPLC/Hb electrophoresis Used to separate and quantify proportions of normal Hb and identify variants FBC Blood film Ferritin due to iron deficiency being a differential for the micro cystic anaemia associated with thalassaemia
39
2 people have their blood tested, one has sickle cells trait and the other has SCD. Assume that both are women. Match the results to the person. Results A: ``` Hb= 130 g/L MCV= Normal MCH= Normal Film= Normal Solubility test= positive HPLC= HbA and HbS ``` ``` Results B: Hb= 70g/L MCV= normocytic MCH= normochromic Film= sickle cells and target cells Solubility test= positive HPLC= HbS ```
``` A= trait B= SCD ```
40
2 people have their blood taken. One has a thalassaemia and the other has an iron deficiency. Match the results to the person. ``` A Hb= Low MCV= 20 MCH= 10 RBC= 6x10 power 12/ L Ferritin= 32g/dL ``` ``` B Hb= Low MCV= 65 MCH= 20 RBC= 4x 10 power 12/L Ferritin= 25g/dL ``` ``` Normal ranges MCV= 80-100 MCH= 27-32 RBC= <5x10 power12/ L Ferritin= 30.5-35g/dL ```
A= thalassaemia I.e. Hb can be normal or low B= iron deficiency
41
What the features of alpha/beta thalassaemia film?
``` Micro cystic/hypo chronic Anisopoikilocyosis Target cells Tear drops Basophilic stippling Fragments Nucleated reds ```
42
How can you differentiated between beta and alpha thalassaemia on screening tests?
HbA2: beta= raised i.e. due to relative lack of beta chains enabling more delta chains to be incorporated to form increased HbA2 Alpha= normal or low
43
How is thalassaemia treated?
Regular blood transfusions 3-4 weekly to prevent extramedullary haematopoiesis Iron chelation therapy Folic acid Prophylactic antibiotics Gene therapy Allogenic stem cell transplant
44
What are the 4 types of sickle cell crisis?
Vaso-occlusive crisis i.e. painful crisis Splenic sequestration crisis Aplastic crisis Acute chest syndrome
45
What causes a sickle cell crisis to occur?
``` Spontaneous Infection Dehydration Cold Significant life events ```
46
How can a sickle cell crisis be managed?
Analgesia i.e. paracetamol or ibuprofen Hydration i.e. IV fluids if worried not getting enough Antibiotics Oxygen Might need penile aspiration in priapism Blood transfusions (look at Hb at indication i.e. <70)
47
When are prophylactic antibiotics given to sickle cell disease patients?
When they have had a splenectomy due to risk of splenic haemorrhage due to splenic sequestration Spleen important for B cell maturation meaning splenectomy leads to patient being immunocompromised
48
What state must sickle cell patient be in in order to receive blood transfusion?
Hb <70 Stable temp and no fever -need to be able to determine whether having reaction to transfusion and pre-existing temp can mask the signs Therefore= need to give paracetamol and fluids to try and decrease temp prior to transfusion
49
What occurs in a vaso-occlusive/painful crisis? What causes this?
Sickle shaped blood cells clog capillaries causing distal ischaemia and can cause priapism in men due to trapping of blood in penis (urological emergency) Causes: -dehydration -raised haematocrit I.e. can occur due to infection
50
What occurs in a splenic sequestration crisis? How is it managed?
RBC block the flow of blood within the spleen causing splenomegaly -sequestration leads to hypovolaemia shock (circulatory collapse) and severe anaemia Blood transfusions and fluid resuscitation I.e. combating the hypovolaemia and anaemia NOTE: - splenectomy can be indicated if patient experiencing recurrent crises
51
What occurs in an aplastic crisis? What causes this?
Temporary loss of new RBC production leading to significant anaemia Cause: -parvovirus B19 (Normally resolves spontaneous within a week but need supportive blood transfusions)
52
How is an acute chest syndrome diagnosed? What causes this? How is it managed?
Fever or resp symptoms New infiltrate seen on CXR Cause: - pneumonia - bronchiolitis - pulmonary vaso-occlusion - fat emboli Managed: - antibiotics if infection - blood transfusions for anaemia - incentive spirometry= encourages effective deep breathing - artificial ventilation i.e. NIV or intubation

Haematology (17 decks)

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