World Sickle Cell Day occours yearly on 19th June to raise awareness of InteSickle-cell disease (SCD), or sickle-cell anaemia (SCA) or drepanocytosis. Sickle Cell disease is a hereditary group of blood disorders typically inherited from a person’s parents. It is characterized by red blood cells that assume an abnormal, rigid, sickleshape. This so called “Sickling” of the red blood cells decreases the cells’ flexibility and results in a risk of various complications. The sickling occurs because of a mutation in the haemoglobin gene. Individuals with one copy of the defunct gene display both normal and abnormal haemoglobin. This is an example of codominance. In 1994, in the US, the average life expectancy of persons with this condition was estimated to be 42 years in males and 48 years in females. The average life expectancy in the developed world is 40 to 60 years However, thanks to better management of the disease, some patients can now live into their 70s or beyond.
The condition was first described in the medical literature by the American physician James B. Herrick in 1910. In 1949, the genetic transmission was determined by E. A. Beet and J. V. Neel. In 1954, the protective effect against malaria of sickle cell trait was described. Sickle-cell disease occurs more commonly among people whose ancestors lived in tropical and sub-tropical sub-saharan regions where malaria is or was common. Where malaria is common, carrying a single sickle-cell gene (sickle cell trait) confers a fitness. Specifically, humans with one of the two alleles of sickle-cell disease show less severe symptoms when infected with malaria.
Sickle-cell anaemia is a form of sickle-cell disease in which there is homozygosity for themutation that causes HbS. Sickle-cell anaemia is also referred to as “HbSS”, “SS disease”, “haemoglobin S” or permutations of those names. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red blood cells. This leads to a rigid, sickle-like shape under certain circumstances.
In heterozygous people, that is, those who have only one sickle gene and one normal adult haemoglobin gene, the condition is referred to as “HbAS” or “sickle cell trait”. Other, rarer forms of sickle-cell disease arecompound heterozygous states in which the person has only one copy of the mutation that causes HbS and one copy of another abnormal haemoglobin allele. They include sickle-haemoglobin C disease (HbSC), sickle beta-plus-thalassaemia (HbS/β+) and sickle beta-zero-thalassaemia (HbS/β0). The term disease is applied because the inherited abnormality causes a pathological condition that can lead to death and severe complications. However Not all inherited variants of haemoglobin are detrimental, a concept known as genetic polymorphism.
Sickle cell disease occurs when a person inherits two abnormal copies of the haemoglobin gene, one from each parent. This gene occurs in chromosome 11. Several subtypes exist, depending on the exact mutation in each haemoglobin gene. An attack can be set off by temperature changes, stress, dehydration and high altitude. A person with a single abnormal copy does not usually have symptoms and is said to have sickle cell trait. Such people are also referred to as carriers. Diagnosis is by a blood test, and some countries test all babies at birth for the disease. Diagnosis is also possible during pregnancy.
Problems in sickle cell disease typically begin around 5 to 6 months of age. A number of health problems may develop, such as attacks of pain (“sickle cell crisis”), anemia, swelling in the hands and feet, bacterial infections and stroke. Long-term pain may develop as people get older. The care of people with sickle cell disease may include infection prevention with vaccination and antibiotics, high fluid intake, folic acid supplementation and pain medication. Other measures may include blood transfusion and the medication hydroxycarbamide (hydroxyurea). A small percentage of people can be cured by a transplant of bone marrow cells. .
As of 2015, about 4.4 million people have sickle cell disease, while an additional 43 million have sickle cell trait.About 80% of sickle cell disease cases are believed to occur in Sub-Saharan Africa. It also occurs relatively frequently in parts of India, the Arabian Peninsula and among people of African origin living in other parts of the world. In 2015, it resulted in about 114,800 deaths.