trioosi

Trioosi is a genetic condition characterized by the presence of three copies of a chromosome in a cell, rather than the usual two. It is a form of aneuploidy and can affect any chromosome. Most cases arise from nondisjunction during meiosis, leading to an extra chromosome in the zygote. Mosaic trioosi, in which only some cells are trisomic, can occur if nondisjunction happens after fertilization.

Clinically, trisomies differ by chromosome and vary in severity and associated features. The best-known forms are trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and trisomy 13 (Patau syndrome). Sex chromosome trisomies include 47,XXX; 47,XXY (Klinefelter syndrome); and 47,XYY.

Diagnosis is often suggested by prenatal screening and confirmed by karyotyping or chromosomal microarray; noninvasive prenatal testing can detect increased likelihood of trisomy. Postnatal diagnosis relies on blood tests and clinical evaluation.

Management depends on the specific trisomy and associated conditions, and typically involves multidisciplinary care, including medical treatment for congenital anomalies, rehabilitation, and developmental support. The prognosis varies widely; some trisomies are compatible with survival into adulthood with varying levels of disability, while others are associated with significant life-threatening complications in early life.

Epidemiology shows that trisomies account for a substantial share of congenital abnormalities and miscarriages; the most common fetal trisomies are 21, 18, and 13. See also trisomy and aneuploidy.