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Sickle Cell Disease

Sickle cell is an autonomic recessive genetic condition that causes sickle-shaped RBCs. It's more common in Afro-Caribbeans. Sickle RBCs are:

  • More fragile and easily destroyed, therefore leading to Haemolytic Anaemia

  • More likely to occlude small vessels


These patients have HbS (Sickle Hb).


HbSS (homozygous) is the most common and severe type of sickle-cell disease. There can also be coinheritance of HbS with other haemoglobin variants, such as HbC or β-thalassaemia, leading to the HbSC or HbS-βthal forms of sickle cell disease. These tend to be a milder version of sickle-cell.


The main complications are:

  • Anaemia (haemolytic) - Jaundice

  • Sickle cell crises

  • Acute chest syndrome

  • Pulmonary HTN

  • Increased risk of infection

  • CKD

  • Avascular necrosis

  • Stroke


Sickle Cell Crises

This occurs spontaneously or is triggered by stresses e.g. infection, dehydration, cold or significant life events. The most common type of crises is a Vaso-occlusive Crisis (AKA painful crisis), which is where this is an occlusion of vessels, resulting in distal ischaemia that is incredibly painful. It's associated with dehydration and raised haematocrit, and can potentially lead to Priapism.


Acute Chest Syndrome is a severe type of vaso-occlusive crisis, causing infarction of lung parenchyma. It's diagnosed by the presence of a fever/respiratory symptoms + new infiltrates on CXR.


Splenic Sequestration Crisis is where there's blocked blood flow to the spleen causing an enlarged, painful spleen, and leading to severe anaemia and hypovolaemic shock. In recurrent cases, a splenectomy is considered. This is associated with a Low Hb + raised reticulocyte count.


Aplastic Crisis is the temporary loss of RBC production, leading to anaemia. It's typically triggered by Parvovirus B19 (also causes slapped cheek syndrome in children – red rash cheeks, spotty rash on torso and limbs). This is associated with a Low Hb + low reticulocyte count.


N.B. Remember that the bone marrow is what produces reticulocytes. As long as it’s working, reticulocytes will be produced as a response to haemolytic anaemia.


Investigations

  • Bloods - Will show microcytic anaemia (reticulocytosis and unconjugated hyperbilirubinemia may also be noted)

  • Blood film - Sickle cells, target cells, reticulocytosis, features of functional hyposplenism (Howell-Jolly bodies, nucleated red blood cells)

  • Hb electrophoresis +/- genetic testing - needed for a definitive diagnosis

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“Sickle-cell disease is a genetic blood disorder characterized by red blood cells that assume an abnormal, rigid, sickle shape” © Dr Graham Beards CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0/)

Management

Typically, the first main things to give patients in acute crisis is Opioid analgesia! Other management includes:

  • Avoid dehydration and other triggers

  • Prophylactic Abx

  • Red cell transfusion

  • Be up to date with vaccinations

  • Bone marrow transplant


In special, chronic cases, Hydroxycarbamide can be given to stimulate the production of HbF (foetal Hb).



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