The sickle cell disease is a genetic disorder caused by an abnormality of hemoglobin (Hb), the mutation in cause having been inherited at the same time from the father and from the mother. Hemoglobinopathies, mainly thalassemia and sickle cell disease are observed worldwide.
The sickle cell disease
1-1.The major sickle cell syndrome
They include various associations responsible for serious syndromes on the clinical and biological plan. We distinguish the homozygous shape SS (or sickle-cell anemia) and compound heterozygous forms connected to the association of the HbS in other hemoglobinopathies (HbS / HbC, HbS / ß thal, HbS / HbD-Punjab, or HbS / HbO-Arab)
1-2. The mecanisms of the desease
Sickle cell disease is related to the presence of an abnormal hemoglobin in the red blood cell: hemoglobin S or HbS. In these patients, slowing the blood flow in the microvasculature allows, under certain conditions (dehydration, hypoxia, acidosis, …), the polymerization of deoxygenated HbS. The polymerization of HbS causes deformation in sickles (sickling) and the stiffening of red blood cells.
The consequences are the obstruction of microvessels (vaso-occlusion) and premature destruction of red blood cells (hemolysis). These two phenomena are at the origin of acute and chronic complications of the disease.
1-3. Clinical signs
Sickle cell disease is characterized by the possible occurrence as young as 3 months of acute complications of variable gravity, and the progressive installation of degenerative hurts and chronic complications. These can develop life-threatening and / or functional. The clinical expression of the disease evolves during the life of patients and is characterized by wide disparities from one patient to another.
Clinical features :
- a chronic hemolytic anemia with potential consequences including the worsening of anemia or the occurrence of gallstones.
- Increased susceptibility to infections by encapsulated bacteria (foreground the Pneumococcus and Salmonella ) due to a hyposplenism.
- vaso-occlusive phenomena dominated by bone crises, and responsible lesions (ischemic) in the organs.
- Infringements of the big vessels (macrovessels) responsible cerebral stroke. These hurts can be detected in children (transcranial Doppler, Nuclear Magnetic Resonance Imaging) to set up a preventive therapeutics based on the realization of exchange transfusion protocols.
Source: Team of the Transversal Sickle Cell Unit of the University Hospital of Pointe-à-Pitre art. Mounlopital