Trisomy 20 Mosaicism
Trisomy 20 Mosaicism - T20M for short - is the name given to a rare chromosome abnormality in which some cells are normal but others are abnormal (hence "mosaicism" - like a tiled floor made up of tiles of two different colours or the picture of flowers below).
The abnormal cells have three copies of chromosome 20 instead of the normal two copies (hence trisomy 20).
Samples for testing can be obtained from many different sources pre-natally. The most common method is by amniocentesis which collects cells in the amniotic fluid which surrounds the fetus in the womb. Pre-natal samples may also be obtained however from the placenta, cord or fetal blood.
Post-natally samples may be obtained from the above, but often also from peripheral blood, skin, and other body organs.
The relative percentages of abnormal to normal cells can vary in any such samples from very low ( e.g. 2%) to very high percentages (e.g. 98%), and can vary from one tissue type to another.
For more information on what the results of the amniocentesis (or CVS) mean click below:
For more information on post-natally confirmed cases of T20M click below:
Post-Natal Confirmed T20M
