Trisomy 16

A genetic disorder caused by an extra copy of chromosome 16

Trisomy 16 is a chromosomal disorder characterized by the presence of an extra copy of chromosome 16. It is one of the most common chromosomal abnormalities observed in miscarriages and is rarely compatible with life.

Genetics

Trisomy 16 occurs when there are three copies of chromosome 16 instead of the usual two. This can happen due to nondisjunction during meiosis, where chromosomes fail to separate properly. The extra chromosome can be present in all cells (full trisomy 16) or in some cells (mosaic trisomy 16).

Diagram of chromosome 16

Clinical Features

Full trisomy 16 is typically not compatible with life and is a common cause of first-trimester miscarriages. Mosaic trisomy 16, where only some cells have the extra chromosome, can result in a live birth but is associated with various developmental and health issues. These may include growth retardation, congenital heart defects, and other anomalies.

Diagnosis

Trisomy 16 can be diagnosed prenatally through procedures such as chorionic villus sampling (CVS) or amniocentesis. These tests analyze fetal cells to detect chromosomal abnormalities.

Micrograph of chorionic villi, which can be sampled for prenatal diagnosis

Prognosis

The prognosis for trisomy 16 depends on whether the condition is full or mosaic. Full trisomy 16 usually results in miscarriage, while mosaic trisomy 16 can lead to a range of outcomes depending on the extent and distribution of the trisomic cells.

Related pages

• Chromosomal disorder
• Nondisjunction
• Prenatal diagnosis

References

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  Chromosome 16
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  Chorionic villi - high magnification