Biology 10 January 2018 Digeorge Syndrome Background Information Digeorge syndrome more commonly known as 22q11 2 deletion syndrome is a disease caused by the deletion of a small part of chromosome 22 The deletion occurs near the center of the chromosome as pictured above Digeorge syndrome was first described in 1968 by Angelo Digeorge which is how it got its name Digeorge syndrome is so broad that in the beginning it went by many different names and because the signs and symptoms of 22q11 2 deletion syndrome are so varied different groupings of features were once described as separate conditions Doctors named these conditions DiGeorge syndrome velocardiofacial syndrome and conotruncal anomaly face syndrome The syndromes received the name of the author that first described each one separately Later with the advance of the diagnostic methods in the field of genetics it was found that the 22q11 2 chromosome was deleted in all of them
They are currently grouped as the 22q11 2 deletion syndromes or Digeorge syndrome because of the difficulties in choosing a single term Digeorge syndrome affects an estimated 1 in 4 000 people This syndrome usually affects children between the age 0 2 as it is a progressive birth defect meaning that the syndrome may not be detected at birth but it will eventually progress to a noticeable state Mechanism The mutation of chromosome 22 plays a role in the development of a number of body systems As a result the disorder can cause several errors during fetal development The deletion of chromosome does not let the fetus grow normally giving it defects In about 10 percent of families the deletion is inherited and other family members are affected or at risk for passing this deletion to their children The gene is autosomal dominant therefore any person who has this deletion has a 50 percent chance of passing the deletion to a child Signs and symptoms The main symptom of 22q11 2 deletion syndrome is heart abnormalities that are often present from birth The deletion highly affects the cardiovascular system and immune system causing a weak immune system and a likely chance of heart issues Children may experience recurrent infections caused by problems with the immune system Some develop autoimmune disorders such as rheumatoid arthritis and Graves disease in which the immune system attacks the body's own tissues and organs
They may also experience breathing problems kidney abnormalities low levels of calcium in the blood which can result in seizures a decrease in blood platelets thrombocytopenia significant feeding difficulties gastrointestinal problems and hearing loss Physical Features Children with Digeorge syndrome do in fact have distinctive facial features Children will have small ears with the upper part of their ear being squared They also may have hooded eyelids along with a cleft lip or palate Also the children may have a small mouth chin and side areas of the nose tip Skeletal differences are possible including mild short stature and less frequently abnormalities of the spinal bones Another obvious facial feature is that the children with 22q11 2 deletion syndrome have asymmetrical crying facies which occurs only in certain circumstances When a baby cries the mouth is pulled downward on one side while not moving on the other side This facial weakness only affects the lower lip as pictured below Asymmetrical crying facies Life Expectancy Children with 22q11 2 deletion syndrome have developmental delays including delayed growth and speech development and learning disabilities Children affected with the 22q11 2 deletion syndrome are more likely to have ADHD or another social disorder on the autism spectrum Later in life they are at an increased risk of developing mental illnesses such as schizophrenia depression anxiety and bipolar disorder Individuals who survive infancy and early childhood have the life expectancy of a normal life span unless they have cardiovascular issues Treatment Although there is no cure for Digeorge syndrome there is treatment for the symptoms Individuals may take vitamins to help with low levels of calcium and take medications to help boost their immune system
They can also get a surgery called Hematopoietic stem cell transplantation in which the stem cells are transplanted to restore one s immune system Individuals may also go to a speech therapists and psychologists to help socially so that they can live their lives as normal as possible Recent Findings As of August 10 2015 children with 22q11 2 deletion syndrome have different patterns of gene expression depending on whether they develop autism or psychosis The study used a special technique for identifying patterns of gene expression it also found that there was an overlap between the differentially expressed genes and those that were studied previously in studies of individuals with idiopathic psychosis and autism Collectively these findings provide a first step toward understanding the functional gene networks disrupted by the 22q11 2 deletion which may relate to variable phenotypic expression of the disorder as stated by the investigators of the study One of the really puzzling things about this disorder and also various other copy number variants is that they are associated with a really high risk of multiple psychiatric disorders said Carrie Bearden PhD the study s senior author and professor of psychiatry and psychology at the University of California Los Angeles UCLA Also an even more recent finding is that dated on July 30 2016 Researchers at the University of California San Diego School of Medicine developed a method to expand the types of chromosomal abnormalities that noninvasive prenatal testing NIPT can detect The study uses a semiconductor sequencing platform to identify small chromosomal deletions or duplications such as occur in DiGeorge Syndrome with a simple blood test from the expectant mother
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