Sickle cell anaemia
What is sickle cell anemia?
Sickle cell anemia is an inherited genetic disease of the blood. More precisely, it affects a component of the cells that carry oxygen in the blood: the hemoglobin of red blood cells.
Sickle cell anemia is the most frequent genetic disease throughout the world. It affects about 1 child in 419 throughout the world. The disease is more prevalent in some parts of the world, particularly in Africa and Asia but also in America (West Indies, Brazil) due to population migration.
The origin of the disease
The disease is present in a patient who has received two copies of the defective gene from their parents leading to the production of non-functional hemoglobin S involved in sickle cell anemia, instead of healthy hemoglobin A. It is autosomal recessive transmission (affecting both girls and boys) recessive. The child will only be affected if both parents are carriers of the gene in question or if one is a carrier and the other parent is affected.
There are different types of sickle cell disease of varying severity. The most severe form, the homozygous form (2 copies of the gene) is the most common form. On the other hand, if the parents only have 1 copy of the gene, the patient is said to be a healthy carrier and has a form of the disease called heterozygous. These patients generally do not have any symptoms.
The diagnosis of sickle cell anemia
Single cell anemia is diagnosed using blood tests. The diagnosis is made when hemoglobin S is detected in the patient's blood.
Due to the production of defective hemoglobin, when the amount of oxygen in the blood increases, hemoglobin S deforms the red blood cells. They then take the form of sickles.
Symptoms of the disease
The manifestations of the disease are of three main types:
- Chronic hemolytic anemia: because of their deformation, red blood cells are weakened and can self-destruct (this is hemolysis). Iron is then poorly transported in the blood and causes anemia. Symptoms are usually pallor (pale skin) and chronic fatigue.
- Very painful vaso-occlusive attacks: in the form of sickle-shaped red blood cells become rigid and can therefore block blood vessels. Pain particularly affects bones, arm and leg joints, back or chest.
- A high risk of developing infections: the spleen, normally in charge of synthesizing infection defence cells, is widely used to destroy deformed red blood cells. It is also one of the locations of vaso-occlusive seizures. As a result, it cannot properly perform its role of protecting against infections.
With these three major symptoms, there is a high individual variability of other symptoms.
The evolution of sickle cell anemia
Acute splenic sequestration
If the spleen begins to destroy more and more red blood cells, this is called acute splenic sequestration. The spleen will therefore not be available to make new red blood cells, which will aggravate the anemia. Splenic sequestration is an absolute vital emergency.
Occlusive seizures can also cause strokes, especially in children. Occlusive seizures can also cause acute chest syndrome. This corresponds to a problem of oxygenation of the whole body due to the occlusion of vessels in the lungs.
Other complications can appear with age: kidney failure, osteoarthritis, osteoporosis, intraocular hemorrhages, pulmonary arterial hypertension, gallstones...
Treatments for sickle cell anemia
The management of sickle cell anemia is based on the prevention of complications because there is no cure for this disease. Regular medical follow-up is essential, including monitoring of kidney, respiratory, eye and blood circulation functions to prevent stroke. It is necessary to prevent infections through vaccination and antibiotic treatments.
Folic acid and iron treatment may be prescribed to reduce the consequences of anemia. In addition, blood transfusions can be performed to increase the red blood cell count.
Simply put, a sickle cell disease patient should have a healthy lifestyle, including proper hydration to reduce painful seizures. These attacks can also be relieved by taking painkillers.
There is now an effective curative treatment, bone marrow transplantation, because it contains the cells that produce red blood cells. This transplant is reserved for the most severe forms of the disease. Sometimes it is difficult to find a donor.
Research is currently underway to develop a gene therapy treatment. This would involve introducing a functional hemoglobin gene into the bone marrow stem cells of affected patients so that the hemoglobin produced is once again functional. Trials are underway in the United States.
Published 15 Oct 2017