Whole chromosome trisomy, mosaicism (mitotic nondisjunction)

This code represents a genetic condition where an individual has an extra copy of an entire chromosome, but this extra chromosome is not present in all cells of the body. Instead, there are at least two different cell lines, one with the normal chromosome number and one with the extra chromosome. This mosaicism arises from a mitotic nondisjunction event after fertilization.

Use this code when diagnostic testing, such as karyotyping or chromosomal microarray, confirms the presence of whole chromosome trisomy in a mosaic pattern. This typically applies to conditions like mosaic Down syndrome (trisomy 21), mosaic Patau syndrome (trisomy 13), or mosaic Edwards syndrome (trisomy 18), where the trisomy is not uniformly present in all cells. Documentation should clearly state "mosaic" or "mosaicism" in conjunction with the specific trisomy.

• Ensure documentation explicitly states "mosaicism" or "mosaic" to differentiate from non-mosaic whole chromosome trisomies.
• Do not use this code for partial trisomies or other chromosomal abnormalities that are not whole chromosome trisomy in a mosaic pattern.
• Sequence this code as the primary diagnosis when the mosaic trisomy is the reason for the encounter or the underlying genetic condition being managed.