Sickle Cell Anaemia

Question 1

What is a sickle syndrome and what does it lead to?

Answer 1

Genetic disorder causing production of HbS, leading to sickle shaped RBCs

Makes the cells more fragile, leading to haemolytic anaemia

Question 2

What causes sickle syndromes?

Answer 2

Autosomal recessive
Point mutation on codon 6 of β globin gene (chromosome 11)
Results in HbS production

Question 3

Pathophysiology of HbS

Answer 3

Polymerises if exposed to low oxygen levels -> RBC distortion -> membrane damage

1 abnormal copy -> trait
Both copies abnormal -> disease

Question 4

What is sickle cell trait?

Answer 4

One normal and one abnormal gene
Asymptomatic, few clinical traits due to low HbS (HbS <50%) levels
May sickle in severe hypoxic situations eg altitude

Question 5

What is sickle cell anaemia?

Answer 5

Two abnormal genes
HbS >80%

May have episodes of tissue infarction due to vascular occlusion, pain may be severe

Precipitated by hypoxia, dehydration, infection, cold, stress

Question 6

What are some other sickle cell diseases?

Answer 6

HbS thalassaemia
HbSC disease- milder but inc thrombosis risk

Question 7

How does sickle cell present?

Answer 7

General anaemia symptoms

Sickle cell crisis if precipitated: (VAAS)

Vaso-occlusive crisis
Aplastic crisis
Acute chest syndrome
Splenic sequestration crisis

Question 8

What are the investigations for sickle cell?

Answer 8

Bloods
Ethnic origin (more common in areas affected by malaria)
HPLC- high performance liquid chromatography, plus electrophoresis, to identify abnormal haemoglobins

Question 9

What is the management for sickle cell anaemia?

Answer 9

Avoid crisis triggers
Prophylactic penicillin in children, and vaccines to protect against infection
Folic acid supplements -> increased RBC turnover
Hydrocycarbamide (aka hydroxyurea) -> inducing HbF production
Crizanlizumab for vast-occlusive crisis

Transfusion for severe anaemia
Bone marrow transplant may be curative

Question 10

What triggers crises in a sickle cell patient?

Answer 10

Dehydration
Infection
Stress
Cold weather

Question 11

What is vaso-occlusive crisis and how does it present?

Also name 1 complication

Answer 11

Most common sickle cell crisis

Caused by sickle shaped cells clogging capillaries, causing distal ischaemia

Presents with peripheral pain and swelling, and possible fever

May also cause priapism (prolonged painful erection, penis requires blood aspiration)

Question 12

What is acute chest syndrome, what causes it, and how is it treated?

Answer 12

Vaso-occlusive crisis of the vessels supplying the lungs

Presentation:
Chest pain and SOB
Fever and hypoxia
Pulmonary infiltrates on X-ray

Supportive treatment:
Analgesia
Hydration
Oxygen therapy
Infection treatment
Transfusions if needed
Incentive spirometry -> machine encouraging good breathing

Question 13

What is Aplastic Crisis?

Answer 13

Temporary absence of RBC production

Usually infective trigger - parvovirus B19

Leads to significant anaemia

Treated supportively

Question 14

What is Splenic Sequestration Crisis?

Answer 14

RBCs blocking flow within spleen, caused by infection eg Strep pneumoniae
Causes acute painful splenomegaly

Can lead to severe anaemia and hypovolaemic shock

Supportive treatment, splenectomy considered in repeat cases

Question 15

Complications of sickle cell disease

Answer 15

Increased infection risk
CKD
Crisis
Stroke
Avascular necrosis in large joints such as the hip
Pulmonary hypertension
Gallstones

Question 16

What is the screening procedure for sickle cell?

Answer 16

Newborn blood spot at 5 days of age

Offered to pregnant women at high risk of being gene carriers