Sickle-cell disease part 03



 Sickle cells  Malaria distribution  Paludisme - Frequence statistique

Note: Sickle cells // Malaria distribution // Paludisme – Frequence statistique

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Africa

Three-quarters of sickle-cell cases occur in Africa. A recent WHO report estimated that around 2% of newborns in Nigeria were affected by sickle cell anaemia, giving a total of 150,000 affected children born every year in Nigeria alone. The carrier frequency ranges between 10% and 40% across equatorial Africa, decreasing to 1–2% on the north African coast and <1% in South Africa. There have been studies in Africa that show a significant decrease in infant mortality rate, ages 2–16 months, because of the sickle-cell trait. This happened in predominant areas of malarial cases.

United States

The number of people with the disease in the United States is approximately 1 in 5,000, mostly affecting Americans of sub-Saharan African descent, according to the National Institutes of Health. In the United States, about one out of 500 African-American children and one in every 36,000 Hispanic-American children have sickle-cell anaemia. It is estimated that sickle-cell disease affects 90,000 Americans. Most infants with SCD born in the United States are now identified by routine neonatal screening. As of 2016 all 50 states include screening for sickle cell disease as part of their newborn screen.

France

As a result of population growth in African-Caribbean regions of overseas France and immigration from North and sub-Saharan Africa to mainland France, sickle-cell disease has become a major health problem in France. SCD has become the most common genetic disease in the country, with an overall birth prevalence of 1/2,415 in Metropolitan France, ahead of phenylketonuria (1/10,862), congenital hypothyroidism (1/3,132), congenital adrenal hyperplasia (1/19,008) and cystic fibrosis (1/5,014) for the same reference period. In 2010, 31.5% of all newborns in Metropolitan France (253,466 out of 805,958) were screened for SCD (this percentage was 19% in 2000). 341 newborns with SCD and 8,744 heterozygous carriers were found representing 1.1% of all newborns in Metropolitan France. The Paris metropolitan district (Île-de-France) is the region that accounts for the largest number of newborns screened for SCD (60% in 2010). The second largest number of at-risk is in Provence-Alpes-Côte d'Azur at nearly 43.2% and the lowest number is in Brittany at 5.5%.

United Kingdom

In the United Kingdom (UK) it is thought that between 12,000 and 15,000 people have sickle cell disease with an estimate of 250,000 carriers of the condition in England alone. As the number of carriers is only estimated, all newborn babies in the UK receive a routine blood test to screen for the condition. Due to many adults in high-risk groups not knowing if they are carriers, pregnant women and both partners in a couple are offered screening so they can get counselling if they have the sickle cell trait. In addition blood donors from those in high-risk groups are also screened to confirm whether they are carriers and whether their blood filters properly. Donors who are found to be carriers are then informed and their blood, while often used for those of the same ethnic group, is not used for those with sickle cell disease who require a blood transfusion.

Middle East

In Saudi Arabia about 4.2% of the population carry the sickle-cell trait and 0.26% have sickle-cell disease. The highest prevalence is in the Eastern province where approximately 17% of the population carry the gene and 1.2% have sickle-cell disease. In 2005 in Saudi Arabia a mandatory pre-marital test including HB electrophoresis was launched and aimed to decrease the incidence of SCD and thalassemia.

In Bahrain a study published in 1998 that covered about 56,000 people in hospitals in Bahrain found that 2% of newborns have sickle cell disease, 18% of the surveyed people have the sickle cell trait, and 24% were carriers of the gene mutation causing the disease. The country began screening of all pregnant women in 1992 and newborns started being tested if the mother was a carrier. In 2004, a law was passed requiring couples planning to get married to undergo free premarital counseling. These programs were accompanied by public education campaigns.

India and Nepal

Sickle-cell disease is common in ethnic groups of central India who share a genetic linkage with African communities, where the prevalence has ranged from 9.4 to 22.2% in endemic areas of Madhya Pradesh, Rajasthan and Chhattisgarh. It is also endemic among Tharu people of Nepal and India; however, they have a sevenfold lower incidence of malaria despite living in a malaria infested zone.

Caribbean Islands

In Jamaica, 10% of the population carries the sickle-cell gene, making it the most prevalent genetic disorder in the country.

History

The first modern report of sickle-cell disease may have been in 1846, where the autopsy of an executed runaway slave was discussed; the key findings was the absence of the spleen. There were also reports amongst African slaves in the United States exhibiting resistance to malaria but being prone to leg ulcers. The abnormal characteristics of the red blood cells, which later lent their name to the condition, was first described by Ernest E. Irons (1877–1959), intern to the Chicago cardiologist and professor of medicine James B. Herrick (1861–1954), in 1910. Irons saw "peculiar elongated and sickle-shaped" cells in the blood of a man named Walter Clement Noel, a 20-year-old first-year dental student from Grenada. Noel had been admitted to the Chicago Presbyterian Hospital in December 1904 suffering from anaemia. Noel was readmitted several times over the next three years for "muscular rheumatism" and "bilious attacks" but completed his studies and returned to the capital of Grenada (St. George's) to practice dentistry. He died of pneumonia in 1916 and is buried in the Catholic cemetery at Sauteurs in the north of Grenada. Shortly after the report by Herrick, another case appeared in the Virginia Medical Semi-Monthly with the same title, "Peculiar Elongated and Sickle-Shaped Red Blood Corpuscles in a Case of Severe Anemia." This article is based on a patient admitted to the University of Virginia Hospital on November 15, 1910. In the later description by Verne Mason in 1922, the name "sickle cell anemia" is first used. Childhood problems related to sickle cells disease were not reported until the 1930s, despite the fact that this cannot have been uncommon in African-American populations.

The Memphis physician Lemuel Diggs, a prolific researcher into sickle cell disease, first introduced the distinction between sickle cell disease and trait in 1933, although it took until 1949 until the genetic characteristics were elucidated by James V. Neel and E.A. Beet. 1949 was the year when Linus Pauling described the unusual chemical behaviour of haemoglobin S, and attributed this to an abnormality in the molecule itself. The actual molecular change in HbS was described in the late 1950s BY Vernon Ingram. The late 1940s and early 1950s saw further understanding in the link between malaria and sickle cell disease. In 1954, the introduction of haemoglobin electrophoresis allowed the discovery of particular subtypes, such as HbSC disease.

Large scale natural history studies and further intervention studies were introduced in the 1970s and 1980s, leading to widespread use of prophylaxis against pneumococcal infections amongst other interventions. Bill Cosby's Emmy-winning 1972 TV movie, To All My Friends on Shore, depicted the story of the parents of a child suffering from sickle-cell disease. The 1990s saw the development of hydroxycarbamide, and reports of cure through bone marrow transplantation appeared in 2007.

Some old texts refer to it as drepanocytosis.

Research

Umbilical cord blood transplant

In December 1998, researchers from Emory University conducted an experimental bone marrow transplant procedure on a group of 22 children under 16 years old. One of those patients, 12-year-old Keone Penn, was apparently the first person to be cured of sickle-cell disease through this method. The stem cells were sourced from a donor unrelated to Penn. A 2007 Georgia Senate bill proposing the collection and donation of stem cell material, the "Saving the Cure Act", was nicknamed "Keone's Law" in his honor.

By mid-2007 a similar set of clinical trials in Baltimore had also cured several adults.

Gene therapy

In 2001 it was reported that sickle-cell disease had been successfully treated in mice using gene therapy. The researchers used a viral vector to make the mice—which have essentially the same defect that causes human sickle cell disease—express production of fetal haemoglobin (HbF), which an individual normally ceases to produce shortly after birth. In humans, using hydroxyurea to stimulate the production of HbF has been known to temporarily alleviate sickle cell disease symptoms. The researchers demonstrated that this gene therapy method is a more permanent way to increase therapeutic HbF production.

Phase 1 clinical trials of gene therapy for sickle cell disease in humans were started in 2014. The clinical trials will assess the safety and initial evidence for efficacy of an autologous transplant of lentiviral vector-modified bone marrow for adults with severe sickle cell disease. As of 2016, however, no randomized controlled trials have been reported. A case report for the first person treated was published in March 2017.

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