Sickle Cell disease Flashcards
What is sickle cell disease?
When red blood cells are more easily destroyed because they are in a sickle shape
this can cause anaemia
What is the primary haemoglobin type affected in sickle cell disease?
HbA - 2 alpha + 2 beta peptide chains
Foetal haemoglobin is not affected by the mutation.
What causes sickle cell disease?
A mutation in the beta globin gene causing the beta chains to be misshapen
What type of disease is sickle cell?
Autosomal recessive
Carriers don’t notice symptoms unless they are exposed to extreme conditions
What is one advantage of sickle cell disease?
It decreases the severity of malaria
How is sickle cell disease tested for?
on the newborn screening heel prick test at 5 days of age.
What is HbS?
Sickle haemoglobin
- 2 alpha chains
- 2 beta (sickle) chains (Both chains have to be mutated)
What extreme conditions can cause sickle carriers to experience symptoms?
High altitude Dehydration Low temperatures Infection (All of these things can set of a sickle cell crisis)
What happens when oxygen is bound to haemoglobin?
The HbS carries oxygen around perfectly well, theres no problems until the oxygen is unbound
What happens when theres no oxygen bound to the HbS?
The haemoglobin changes its shape and binds to other proteins causing the red blood cell to become a present shape = sickling
How are RBCs destroyed?
2/3rds are destroyed extravascularly
1/3rd is destroyed intravascularly
Where does free haemoglobin after haemolysis go?
Binds to haptoglobin.
Low haptoglobin is a sign of sickle cell disease
What does low haptoglobin show?
Intravascular haemolysis is occurring
What are signs/complications of sickle cell disease?
Dactylitis (sickle cells getting blocked in small blood vessels in the digits)
Pain crisis
Avacsular necrosis
Increased bone formation (increased bone marrow to try and increase more RBCs)
Hepatomegaly (liver also tries to make RBCs)
Splenic infarcts
Splenomegaly
Infection
Strokes
Haematuria
Gallstones
What investigations can be done for sickle cell disease?
Blood smear - shows sickle cells
Protein electrophoresis - identifies HbS
What is the treatment for sickle cell disease?
Opioids Oxygen Fluids Antibiotics Folic acid Blood transfusions (*risk of iron overload + production of antibodies against future transfusions)
Children - prophylaxis penicillin
What is a carrier of one sickle cell gene called?
Sickle cell trait.
When do symptoms of sickle cell disease begin to show?
Usually at 4-6 months (because this is when the foetal haemoglobin runs out and the patient relies on their HbA, which is actually HbS).
Why are sickle cell patients more prone to bacterial infections?
Because the spleen is overwhelmed with too many red blood cells, meaning it cannot phagocytose as much bacteria as it usually would.
What are the types of sickle cell crisis?
Vaso occlusive crisis
Acute chest syndrome
Aplastic crisis
Splenic sequestration crisis
what is a common cause of aplastic crisis?
Parvovirus B19.
What type of anaemia is sickle cell disease?
Microcytic anaemia.
what is the main treatment for a sickle cell crisis?
Oxygen (15L via non rebreathe mask) IV fluids Keep patient warm Antibiotics Aspiration (for priapism) Blood transfusion (For aplastic crisis)
Refer to haematology
What is an aplastic crisis?
when the bone marrow doesn’t make enough red blood cells
what is a sequestration crisis?
when the spleen is enlarged due to a build up of sickle cells
What is acute chest syndrome?
A vaso occlusive crisis in the lungs brought on by infection
(Fever OR Respiratory symptoms) + Infiltrates seen on CXR
What is a vaso occlusive crisis?
when sickled red blood cells cause a blockage in blood flow through the vessels
(Often results in avascular necrosis of bones and organ damage).
what is a common urogenital emergency associated with sickle cell crisis?
Priapism - a prolonged and painful erection of the penis. Treated by urgent aspiration
