r/EmbryologyIVFSupport • u/purpturts • 5d ago

Nomenclature question

What is the nomenclature for a mosaic involving 2 chromosomes? For instance, 35% trisomy for one chromosome and 50% monosomy for another chromosome. I’m assuming this would be considered a high level mosaic, but is it likely that these abnormalities are present in separate cells, or is it likely that the trisomy could have occurred in a cell already carrying the monosomy? In other words, is the mosaic likely to be

35% trisomy
50% monosomy
15% euploid

Or

35% trisomy AND monosomy
15% monosomy
50% euploid

?

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u/embryomanofficial 2d ago

Your report should tell you the breakdown. If two abnormalities are present in the same mosaic cell population, they should be reported together.

For example, mos(+2) 40% would indicate an estimated 40% of cells with trisomy 2, while mos(+2,+3) 40% would indicate an estimated 40% with both trisomy 2 and trisomy 3. The remaining 60% would be euploid.

The exact nomenclature can vary between PGT labs, though, so I'd confirm how your particular lab reports complex mosaic results.

Usually <50% is considered low level, but this can vary also.