Sickle-cell anaemia Flashcards
What is sickle cell anaemia?
Autosomal recessive condition that causes sickle (crescent) shaped red blood cells.
What type of inheritance does sickle cell anaemia have?
Autosomal recessive
What do red blood cells being sickle shaped mean?
It means they are fragile and more easily destroyed leading to an haemolytic anaemia.
What are patients with sickle cell anaemia prone to?
Sickle cell crises
What is the genetic cause of sickle cell anaemia?
Glutamic acid is replaced by valine on the 6th position of the β chain.
Resulting in an abnormal gene for beta-globin on chromosome 11
What type of mutation results in sickle cell anaemia?
Point mutation
What does one copy of the abnormal gene result in?
Sickle cell trait Hb AS (carrier)
What is required for sickle cell disease?
Two abnormal copies of the gene HbSS
How is sickle cell anaemia diagnosed in a new born?
Heel prick test at 5 days of age
Who would be offered a gene test?
Women at risk of being carries are offered a gene test when pregnant
What are some possible complications of sickle cell anaemia?
- Anaemia
- Increased risk of infection (due to hyposplenism)
- Stroke (one of the commonest causes in children)
- Avascular necrosis in large joints such as the hip
- Pulmonary hypertension
- Priapism
- Chronic kidney disease
- Sickle cell crises
- Acute chest syndrome
What are sickle cell crises?
An umbrella term for a spectrum of acute crises related to the condition.
How can sickle cell crises occur?
They can be spontaneous
Or
Triggered by stresses- infection, dehydration, cold or significant life events.
What are some examples of sickle cell crises?
- thrombotic, ‘painful crises’
- sequestration
- acute chest syndrome
- aplastic
- haemolytic
What is the most common acute presentation of sickle cell crises?
Thrombotic crises (Vaso-occlusive Crisis (AKA painful crisis))
What is the cause of thrombotic crises?
sickle shaped blood cells clogging capillaries causing distal ischaemia
What can thrombotic crises cause in men?
Priapism
What is Priapism?
Blood is trapped in the penis causing a painful and persistent erection
What is the management of Priapism?
Urological emergency
Treated with aspiration of blood from the penis.
What is Sequestration crises?
Sickling within organs such as the spleen or lungs causes pooling of blood with worsening of the anaemia
What is sequestration crises associated with?
An increased reticulocyte count
What is acute chest syndrome?
Most dangerous acute presentation of sickle cell anaemia
How does acute chest syndrome present?
- Tachypnoea
- Wheeze
- Cough
- Pulmonary infiltrates
- Hypoxia-low pO2
What acute chest syndrome the most common cause of?
Death after childhood
What is seen on chest x ray of someone with acute chest syndrome?
New infiltrates seen on a chest x-ray
What happens when a blood cell goes into hypoxic tissue in someone with sickle cell anaemia?
The RBC change from biconcave to sickle cell shape
What is the management of sickle cell crises?
analgesia e.g. opiates
rehydrate
oxygen
consider antibiotics if evidence of infection
blood transfusion
exchange transfusion: e.g. if neurological complications
When would you carry out exchange transfusion?
If there are neurological complications
What would you give if there was evidence of infection in a sickle cell crises?
Antibiotics
What is long term prophylaxis for sickle cell anaemia?
Hydroxyurea
What is the function of hydroxyurea?
Increase HbF levels
Prevents painful episodes
What should patient receive every 5 years?
pneumococcal polysaccharide vaccine
