11/21/2023 0 Comments Abnormal q![]() The loss of additional genes in the deleted region likely contributes to the varied features of 22q11.2 deletion syndrome. The loss of another gene, COMT, in the same region of chromosome 22 may also help explain the increased risk of behavioral problems and mental illness. Some studies suggest that a deletion of this gene may contribute to behavioral problems as well. ![]() They have determined that the loss of a particular gene on chromosome 22, TBX1, is probably responsible for many of the syndrome's characteristic signs (such as heart defects, a cleft palate, distinctive facial features, hearing loss, and low calcium levels). Researchers are working to identify all of the genes that contribute to the features of 22q11.2 deletion syndrome. This condition is described as a contiguous gene deletion syndrome because it results from the loss of many genes that are close together. A small percentage of affected individuals have shorter deletions in the same region. This region contains 30 to 40 genes, many of which have not been well characterized. ![]() Most people with 22q11.2 deletion syndrome are missing a sequence of about 3 million DNA building blocks ( base pairs ) on one copy of chromosome 22 in each cell. To avoid confusion, this condition is usually called 22q11.2 deletion syndrome, a description based on its underlying genetic cause. Once the genetic basis for these disorders was identified, doctors determined that they were all part of a single syndrome with many possible signs and symptoms. In addition, some children with the 22q11.2 deletion were diagnosed with the autosomal dominant form of Opitz G/BBB syndrome and Cayler cardiofacial syndrome. Doctors named these conditions DiGeorge syndrome, velocardiofacial syndrome (also called Shprintzen syndrome), and conotruncal anomaly face syndrome. Additionally, affected children are more likely than children without 22q11.2 deletion syndrome to have attention-deficit/hyperactivity disorder (ADHD) and developmental conditions such as autism spectrum disorder that affect communication and social interaction.īecause the signs and symptoms of 22q11.2 deletion syndrome are so varied, different groupings of features were once described as separate conditions. Children with this condition often need help changing and adapting their behaviors when responding to situations. Older affected individuals have difficulty reading, performing tasks involving math, and problem solving. Many children with 22q11.2 deletion syndrome have developmental delays, including delayed growth and speech development, and some have mild intellectual disability or learning disabilities. Skeletal differences are possible, including mild short stature and, less frequently, abnormalities of the spinal bones. Affected individuals may also have 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. Submucosal cleft palate can also interfere with normal speech by causing air to come out of the nose during speech, leading to nasal-sounding speech. The abnormal palate is often highly arched and there may be a split in the soft flap of tissue that hangs from the back of the mouth ( bifid uvula ). In affected individuals, the muscles that form the roof of the mouth (palate) may not close completely, even though the tissue covering them does, resulting in a condition called submucosal cleft palate. People with 22q11.2 deletion syndrome commonly have heart abnormalities that are often present from birth, recurrent infections caused by problems with the immune system, and distinctive facial features. The features of this syndrome vary widely, even among affected members of the same family. The deletion occurs near the middle of the chromosome at a location designated q11.2.Ģ2q11.2 deletion syndrome has many possible signs and symptoms that can affect almost any part of the body. 22q11.2 deletion syndrome (which is also known by several other names, listed below) is a disorder caused by the deletion of a small piece of chromosome 22.
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