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  • DiGeorge syndrome

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    DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by the deletion of a small segment of chromosome 22. While the symptoms can be variable, they often include congenital heart problems, specific facial features, frequent infections, developmental delay, learning problems and cleft palate. Associated conditions include kidney problems, hearing loss and autoimmune disorders such as rheumatoid arthritis or Graves disease. DiGeorge syndrome is typically due to the deletion of 30 to 40 genes in the middle of chromosome 22 at a location known as 22q11.2. About 90% of cases occur due to a new mutation during early development, while 10% are inherited from a person's parents. It is autosomal dominant, meaning that only one affected chromosome is needed for the condition to occur. Diagnosis is suspected based on the symptoms and confirmed by genetic testing. Although there is no cure, treatment can improve symptoms. This often includes a multidisciplinary approach with efforts to improve the function of the potentially many organ systems involved. Long-term outcomes depend on the symptoms present and the severity of the heart and immune system problems. With treatment, life expectancy may be normal. DiGeorge syndrome occurs in about 1 in 4,000 people. The syndrome was first described in 1968 by American physician Angelo DiGeorge. In late 1981, the underlying genetics were determined.

  • Rett syndrome

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    Rett syndrome (RTT) is a genetic brain disorder which typically becomes apparent after 6 to 18 months of age in females. Symptoms include problems with language, coordination, and repetitive movements. Often there is slower growth, problems walking, and a smaller head size. Complications can include seizures, scoliosis, and sleeping problems. Those affected, however, may be affected to different degrees. Rett syndrome is due to a genetic mutation of the MECP2 gene. This gene occurs on the X chromosome. Typically it develops as a new mutation, with less than one percent of cases being inherited from a person's parents. It occurs almost exclusively in girls. Boys who have a similar mutation typically die shortly after birth. Diagnosis is based on symptoms and can be confirmed with genetic testing. There is no known cure for Rett syndrome. Treatment is directed at improving symptoms. Anticonvulsants may be used to help with seizures. Special education, physiotherapy, and braces may also be useful. Many people with the condition live into middle age. The condition affects about 1 in 8,500 females. Andreas Rett, a pediatrician in Vienna, first described the condition in 1966. As his writings were in German, they did not become widely known in the English-speaking world. Bengt Hagberg, a Swedish pediatrician, published an English article in 1983 and named the condition after Rett. In 1999, Lebanese-American physician Huda Zoghbi discovered the mutation that causes the condition.

  • Down syndrome

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    Down syndrome (DS or DNS), also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental ability of an 8- or 9-year-old child, but this can vary widely. The parents of the affected individual are typically genetically normal. The probability increases from less than 0.1% in 20-year-old mothers to 3% in those age 45. The extra chromosome is believed to occur by chance, with no known behavioral activity or environmental factor that changes the probability. Down syndrome can be identified during pregnancy by prenatal screening followed by diagnostic testing or after birth by direct observation and genetic testing. Since the introduction of screening, pregnancies with the diagnosis are often terminated. Regular screening for health problems common in Down syndrome is recommended throughout the person's life. There is no cure for Down syndrome. Education and proper care have been shown to improve quality of life. Some children with Down syndrome are educated in typical school classes, while others require more specialized education. Some individuals with Down syndrome graduate from high school, and a few attend post-secondary education. In adulthood, about 20% in the United States do paid work in some capacity, with many requiring a sheltered work environment. Support in financial and legal matters is often needed. Life expectancy is around 50 to 60 years in the developed world with proper health care. Down syndrome is one of the most common chromosome abnormalities in humans. It occurs in about one per 1,000 babies born each year. In 2015, Down syndrome was present in 5.4 million individuals and resulted in 27,000 deaths, down from 43,000 deaths in 1990. It is named after John Langdon Down, a British doctor who fully described the syndrome in 1866. Some aspects of the condition were described earlier by Jean-Étienne Dominique Esquirol in 1838 and Édouard Séguin in 1844. In 1959, the genetic cause of Down syndrome, an extra copy of chromosome 21, was discovered.

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