People have 23 pairs of chromosomes. Tri-somy means three-chromosomes. Trisomy 13 means there’s an extra chromosome kickin’ it with chromosome pair 13 (Down Syndrome is Trisomy 21; extra chromosome on pair 21). Get it? Trisomy 13 is also known as Patau Syndrome (named after the dude who first ascertained T13).
Variations of Trisomy:
Complete + Partial (chromosome)
Complete and partial characterize the extra chromosome. Complete refers to an entire chromosome being copied. Partial refers to some of the chromosome being copied.
Full + Mosaic (cell)
Full and mosaic characterize the cell. Full means every cell in the body has trisomy (an extra chromosome) regardless of whether it’s complete or partial.
Mosaic means some cells have a well organized 23 pairs and some cells didn’t get their shit together and there’s a tag along (extra), also regardless of whether it’s complete or partial. Because cells die and new ones are made, the number of trisomy cells can change and it’s impossible to do tests to find out an accurate number. (You’d have to test every single ever-changing cell in the body, forever…simply impossible.) It’s safe to assume, anywhere there is a defect or anomaly, there is a higher number of trisomy cells. Being mosaic means a person has two different genetic makeups.
Isodicentric characterizes the arrangement of the extra chromosome. Isodicentric means the extra chromosome is mirror imaged and stuck to its pair. (It’s a copycat with attachment issues).
Complete Isodicentric Trisomy 13 Mosaicism
Liam has an extra, complete chromosome, mirror imaged on pair 13 in most of his cells. His tests showed over 80% of his blood has Trisomy 13 cells.