Whole chromosome trisomy, nonmosaic (meiotic nondisjunction)

This code signifies a genetic condition characterized by the presence of an extra whole chromosome in every cell of the body, resulting from an error during meiosis (nondisjunction). This chromosomal abnormality is not mosaic, meaning all cells are affected, rather than a mixture of normal and abnormal cells. It represents a constitutional trisomy, such as Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome), or Trisomy 13 (Patau syndrome).

Use this code for patients diagnosed with a nonmosaic whole chromosome trisomy confirmed by karyotype analysis. This applies when the genetic testing indicates that the extra chromosome is present in all cells examined, ruling out mosaicism. Documentation should clearly state the specific trisomy and confirm its nonmosaic nature.

• Ensure documentation specifies "nonmosaic" to differentiate from mosaic trisomies (Q92.1).
• Always sequence this code first when it represents the primary reason for the encounter or the underlying genetic cause of other conditions.
• Do not use this code for partial trisomies or other complex chromosomal rearrangements; specific codes exist for those conditions.