Quesmed (sickle cell disease) Flashcards
What is sickle cell disease?
A genetic condition where normal haemoglobin (where variable HbS is present) tends to form abnormal haemoglobin molecules (HbS) upon deoxygenation leading to distortion of RBCs.
Who is sickle cell anaemia commonly present in and why is this?
Common among individuals of Central and West African descent, where having the carrier (trait) status confers some protection against malaria.
How is HbS produced?
HbS is produced when the glutamic acid at the 6th position of the β chain is replaced by valine
Inheritance pattern for sickle cell anaemia?
autosomal recessive condition
What is hyposplenism?
Reduced spleen function, this is not as bad as asplenia which is complete absence of spleen function.
How does hyposplenism occur in sickle cell anaemia?
Sickled red cells commonly sequester in the spleen, where they undergo phagocytosis by the reticular endothelial system, leading to extravascular haemolysis.
Initially, this leads to splenic congestion and splenomegaly
This is followed by splenic infarction, leading to hyposplenism
What is the most common acute presentation of sickle cell disease?
Vaso-occlusive crisis (painful)
Features of vaso-occlusive crisis?
Primarily caused by microvascular obstruction due to RBC sickling and inflammation
May be triggered by local hypoxia (eg. in cold weather)
What is the most dangerous acute presentation for sickle cell disease?
Acute chest crisis
Cause of acute chest crisis in sickle cell disease?
The cause is often unknown (maybe infectious)
Presenting features of acute chest crisis?
Tachypnoea, wheeze, and cough, with hypoxia and pulmonary infiltrates on chest X-ray
Investigations for sickle cell disease?
Bedside - peak flow, which is essential for monitoring patients with chest crisis
FBC may show microcytic anaemia with variable degrees of haemolysis
Reticulocytosis and unconjugated hyperbilirubinemia may be noted
Blood film features of sickle cell disease?
Characteristic sickle cells
Target cells
Reticulocytosis with polychromasia
Features of functional hyposplenism (Howell–Jolly bodies, nucleated red cells)
Definitive diagnosis for sickle cell disease?
Haemoglobin electrophoresis +/– genetic testing
Treatment of acute sickle cell crisis?
High-flow oxygen
IV fluids and analgesia
Top-up transfusions – required in some severe cases
