Q91.5 — Trisomy 13, mosaicism (mitotic nondisjunction)
Q91.5 is a billable, specific ICD-10-CM code for trisomy 13, mosaicism (mitotic nondisjunction). It is valid for submission on a claim.
Risk adjustment
Q91.5 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.
Medicare coverage
Q91.5 is named in 3 Medicare coverage policies — 3 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A56781Billing and Coding: Transthoracic Echocardiography (TTE)
- A57204Billing and Coding: MRI and CT Scans of the Head and Neck
- A57306Billing and Coding: Transthoracic Echocardiography (TTE)
How Q91.5 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to Q91.5.
- Trisomy›13›mitotic nondisjunction
- Trisomy›13›mosaicism
- Syndrome›trisomy›13›mitotic nondisjunction
- Syndrome›trisomy›13›mosaicism
Related codes at this level
Codes that share Q91. If Q91.5 is not quite right, the correct code is usually one of these.
Questions about Q91.5
- Is Q91.5 a billable ICD-10-CM code?
- Yes. Q91.5 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does Q91.5 sit in the tabular list?
- Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0), in the block Chromosomal abnormalities, not elsewhere classified (Q90-Q99).