ICD-10-CM 2027
ICD-10 code for down syndrome
From the official ICD-10-CM alphabetic index entry “Down syndrome”. Page updated September 29, 2026.
About coding down syndrome
The ICD-10-CM code for down syndrome is Q90.9 (Down syndrome, unspecified). The official index lists 4 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on Q90.9.
Within Q90, choose Q90.9 (unspecified) only when documentation doesn't support a more specific option: trisomy 21, nonmosaicism (meiotic nondisjunction) (Q90.0), trisomy 21, mosaicism (mitotic nondisjunction) (Q90.1) and trisomy 21, translocation (Q90.2).
Use an additional code(s) to identify any associated degree of intellectual disabilities (F70-F79).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
More specific down syndrome codes (official index)
Common questions about down syndrome ICD-10 codes
What is the ICD-10 code for down syndrome?
- Q90.9 — Down syndrome, unspecified. More specific codes apply when the documentation supports them: Q90.0, Q90.1, Q90.1, Q90.2.
What is the ICD-10 code for meiotic nondisjunction down syndrome?
- Q90.0 — Trisomy 21, nonmosaicism (meiotic nondisjunction).
What is the ICD-10 code for mitotic nondisjunction down syndrome?
- Q90.1 — Trisomy 21, mosaicism (mitotic nondisjunction).
What is the ICD-10 code for mosaicism down syndrome?
- Q90.1 — Trisomy 21, mosaicism (mitotic nondisjunction).
What is the ICD-10 code for translocation down syndrome?
- Q90.2 — Trisomy 21, translocation.
Is Q90.9 billable?
- Yes. Q90.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Q90.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict Q90.9 as a principal diagnosis.
Is Q90.9 a CC or MCC?
- No. Q90.9 is neither a CC nor an MCC under MS-DRG v44.0.