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Hemoglobinopathies- WB5 > Sickle Cell Disease > Flashcards

Sickle Cell Disease Flashcards

1
Q

Pathogenesis of HbS?

A

Single point mutation in the Hb synthesis where Valine replaces Glutamic acid at position 6 in the beta chain.

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2
Q

Pathogenesis of HbC

A

Lysine replaces Glutamic acid at point 6 of Chromosome 11

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3
Q

How is the Sickling test performed?

A

2% Sodium metasulphite is added to the blood to indicate presence of HbS

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4
Q

Exceptions to Sickling test

A

Not useful in newborns
Results are either negative or positive

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5
Q

What test is definite for Hemoglobinopathies?

A

HB electorphoresis

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6
Q

What is HB electrophoresis?

A

It is a separation test.
Cellulose acetate electrophoresis pH 8.6 is the commonest.

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7
Q

How do you use Hb electrophoresis to diagnose thalassemia?

A

HbA2 > 5% shows thalassemic trait.

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8
Q

How do you diagnose Sickle cell?

A

Sickling test
HB electrophoresis
Fetal blood sampling ( pre- natal diagnosis)

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9
Q

What factors affect severity of SCD?

A
  1. Levels of HbF
  2. Other associated RBC enzyme deficiency like G6PD deficiency which leads to repeated hemolysis.
  3. Environment. Infections precipitate crisis
  4. Good nutrition and prompt medical care
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10
Q

Clinical presentation of SCD?

A

-Pain
- Bacteremia- early part of life.
- Acute chest syndrome- childhood to adolescence.
- Acute sequestration crises- 10years
- Stroke
-Chronic organ damage.

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11
Q

Signs of SCD in childhood.

A

Pallor
Jaundice
Hepatosplenomegaly
Hand and foot syndrome (dactylitis)
Painful swollen feet and hands

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12
Q

Examples of recurrent episodes of Acute events

A
  1. Vaso-Occlusive Pain Crisis (VOPE)
  2. Infarctive crises
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13
Q

What is VOPE?

A

Occlusion of vessels by sickled cells resulting in pain from ischemic tissue injury/infarction.
Release of inflammatory mediators, activation of afferent nerve fibers.
Mostly affects long bones, abdomen, chest and back.

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14
Q

Causes of VOPE?

A

Infection
Physical exertion
Exposure to extremes of weather
Fever
Dehydration

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15
Q

X’tics of infarction crises

A

Bone pain
Acute abdominal pain(acute cholecystitis)
Acute chest syndrome
Priapism

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16
Q

How do you manage pain crises?

A
  1. Identify and treat underlying cause
  2. Hydration- oral/IV infusion(D/S or N/S) at one and half maintenance.
  3. Analgesics based on severity of pain
  4. Massaging,
  5. Application of heat
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17
Q

What analgesics do you give in Pain crises?

A
  1. Mild- non opioids like p’mol,
  2. Moderate- NSAIDs + p’mol
  3. Severe- opioids
18
Q

Features of Acute Anemic Episodes

A

1 Hyperhemolytic crisis
2. Aplastic Crises
3. Acute sequestration crises
4. Megaloblastic changes

19
Q

What is Hyperhemolytic crises?

A

Life span of HbS rbc is 10-20 days
Causes: infection, G6PD deficiency which worsens the hemolysis.

20
Q

Features of Hyperhemolytic crises

A

Low Hb, PCV
Increased retic count
Pallor
Hepatosplenomegaly
Jaundice
Cola-like urine

21
Q

What is Aplastic crises?

A

Acute failure of erythropoiesis

22
Q

Features of aplastic crises

A

Low Hb, PCV,
Low or absent retic count
Ass with parvovirus B19 infection

23
Q

Treatment for Aplastic crises

A

Packed rbc transfusion

24
Q

What is Acute sequestration crises?

A

Sudden progressive anemia accompanied by painful splenic enlargement and hypovolemic shock due to pooling of blood in the spleen which results in splenomegaly by >2cm and drop in Hb > 2 gm
This can also occur in the liver

25
Q

Clinical presentation of acute chest syndrome

A

Chest pain
Fever
Signs of respiratory distress
New pulmonary infiltrate on chest X-ray

26
Q

What megaloblastic changes occur in SCD?

A

Chronic hemolysis leads to folate deficiency

27
Q

How is acute chest syndrome managed?

A

Clinically treated as infection (pneumonia) or infarction
Broad spectrum Antibiotics + macrolides
Analgesics
Hydration
Oxygen/ventilation
Chest physiotherapy + incentive spirometry
Bronchodilators
Blood Transfusion
Steroids-

28
Q

What makes one susceptible to infections?

A

Splenic hypo function
Defective opsonization
Abnormal phagocytic function against encapsulated organisms, pneumococcus and salmonella
Impaired humoral antibody response
Necrotic tissue from recurrent vaso-occlusion esp in salmonella osteomyelitis.

29
Q

How do you manage pneumococcal infection?

A

Penicillin prophylaxis after 8 weeks of life
Oral penicillin (125mg po BID for all children < 3 years), 250 mg BID for children > 2 years

Vaccines: pneumovax

30
Q

How do you manage pneumococcal infection?

A

Penicillin prophylaxis after 8 weeks of life
Oral penicillin (125mg po BID for all children < 3 years), 250 mg BID for children > 2 years

Vaccines: pneumovax
Prevar vaccine

31
Q

Presentation of SCD in the Genitourinary System

A

Renal
Priapism

32
Q

Renal manifestations

A
  1. Papillary necrosis- loss of concentration ability
  2. Hyposthenuria( low SG of urine) leading to polyuria, nocturia and enuresis
  3. Nephrotic syndrome
  4. Renal infarction
  5. Pyelonephritis
  6. Renal modeling carcinoma
33
Q

Priapism

A

2 types
1. Stuttering- short- lasting/ self - limiting bouts with many episodes
2. Major episode/ refractory
May lead to impotence

34
Q

Treatment of Genitourinary manifestations

A
  • conservative pain relief, hydration, transfusion, alkalization, exercises, hot baths.
  • Surgery
35
Q

Bone and Joint manifestations

A
  1. Bone marrow expansion
    Increased erythropoiesis -> frontal/ bossing, gnathopathy.
  2. Avascular necrosis- especially of the femoral head.
  3. Osteomyelitis- humerus, radius, ulna, femur. Salmonella, staph aureus.
  4. Leg ulcers- common in adolescents and young adults. Malleolar areas
36
Q

Eye manifestations

A

Retinopathy- retinal detachment

37
Q

Growth manifestations

A

Delayed puberty by 2 years
Poor and stunted growth

38
Q

CNS manifestations

A
  • headache
  • Stroke
  • convulsions
  • drowsiness
  • coma dysphasia
  • visual disturbance
  • hemiplegia, monoplegia, tetraplegia
  • child with painless limp
  • infarctive stroke- occlusion of vessels
  • moya moya: hemorrhagic stroke-> rupture of aneurysms formed in the circle of willis.
39
Q

Outcome of stroke in SCD

A
  1. Immediate
  2. Long term neurologic outcome
40
Q

Stroke prevention

A

Chronic transfusion
Hydroxyurea

41
Q

Outcome of transfusion therapy

A

Iron overload

42
Q

How is stroke managed in SCD?

A

Transcranial Doppler ultrasound
t - ICA/MCA velocity
- Normal < 170cm/s
- conditional > 170cm/s < 200cm/s
- Abnormal > 200cm/s leads to chronic transfusion therapy/ Hydroxyurea therapy
Headaches
High Hb > 10

  • increase HbF - Hydroxyurea
    Voxeletol (oxybryte)

Hemoglobinopathies- WB5 (3 decks)

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