Tetrasomies

Tetrasomy is a type of aneuploidy, which is an abnormal number of chromosomes. In tetrasomy, there are four copies of a particular chromosome instead of the usual pair. This means an individual with a tetrasomy has a total of 47 chromosomes in each cell, with one chromosome being present in four copies and the other 22 pairs present in two copies, for a total of 47 chromosomes. Tetrasomies can occur with any chromosome, but some are more common than others.

The most frequently observed tetrasomy in humans is Tetrasomy 18p. This condition is characterized by a specific set of physical and developmental features. Individuals with Tetrasomy 18p may experience intellectual disability, developmental delays, distinctive facial features, and sometimes heart defects or other organ abnormalities. The severity of symptoms can vary widely among affected individuals.

Tetrasomy is typically caused by errors during cell division, specifically in meiosis, the process that produces egg and sperm cells. When chromosomes fail to separate properly during meiosis, the resulting gamete can have an extra copy of a chromosome. If this gamete is involved in fertilization, the resulting embryo will have three copies of that chromosome, leading to a trisomy. In rare cases, further errors can lead to a tetrasomy, where the chromosome is present in four copies.

Diagnosis of tetrasomy is usually made through genetic testing, such as karyotyping or chromosomal microarray analysis, which can detect the extra chromosome. There is no cure for tetrasomies, and treatment focuses on managing the symptoms and providing supportive care to improve the quality of life for affected individuals. Early intervention services, therapies, and medical management of associated health issues are crucial for individuals with tetrasomies.