Q90.1 — Trisomy 21, mosaicism (mitotic nondisjunction)
Q90.1 is a billable, specific ICD-10-CM code for trisomy 21, mosaicism (mitotic nondisjunction). It is valid for submission on a claim.
Risk adjustment
Q90.1 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
Q90.1 is named in 5 Medicare coverage policies — 5 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A54111Billing and Coding: Speech Language Pathology (SLP) Services: Communication Disorders
- A56781Billing and Coding: Transthoracic Echocardiography (TTE)
- A56781Billing and Coding: Transthoracic Echocardiography (TTE)
- A57306Billing and Coding: Transthoracic Echocardiography (TTE)
How Q90.1 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 Q90.1.
- Down syndrome›mitotic nondisjunction
- Down syndrome›mosaicism
- Trisomy›21›mitotic nondisjunction
- Trisomy›21›mosaicism
- Syndrome›trisomy›21›mitotic nondisjunction
- Syndrome›trisomy›21›mosaicism
Related codes at this level
Codes that share Q90. If Q90.1 is not quite right, the correct code is usually one of these.
Questions about Q90.1
- Is Q90.1 a billable ICD-10-CM code?
- Yes. Q90.1 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does Q90.1 sit in the tabular list?
- Congenital malformations, deformations and chromosomal abnormalities (Q00-QA0), in the block Chromosomal abnormalities, not elsewhere classified (Q90-Q99).