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
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).