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Q90.9 ICD-10-CM Code: Down syndrome, unspecified

Billing Status: YES. This is a valid, specific, and billable ICD-10-CM reference.

Coding at a Glance

Tabular directives
1 inclusion term · 1 Excludes2 · 1 use-additional code · 1 code-also instruction

Inpatient Payment Groups (MS-DRG)

Potential MS-DRG participation — not a DRG assignment.

MS-DRGs this diagnosis helps define, as principal or secondary, per the CMS ICD-10-CM/PCS MS-DRG Definitions Manual v43, Appendix B.

  • MS-DRG 884 — ORGANIC DISTURBANCES AND INTELLECTUAL DISABILITY (MDC 19)

A diagnosis appearing in a group's logic does not by itself determine the DRG assigned to a stay; the grouper uses the full claim.

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Q90.9 in the official ICD-10-CM tabular list, quoted as published.

Source: CMS/CDC — ICD-10-CM Tabular ListRelease: FY2026Effective: October 1, 2025

Notes without a marker are published on Q90.9 itself; “inherited from” names the category or block whose note applies here.

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Trisomy 21 NOS

Excludes2 — Not Included Here

Conditions not covered by this code, but which may be reported alongside it when both are present.

Source: inherited from Q90-Q99

Code Also

Additional codes that may be required to fully describe the encounter.

  • associated physical condition(s), such as atrioventricular septal defect (Q21.2-)

Source: inherited from Q90

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code(s) to identify any associated degree of intellectual disabilities (F70-F79)

Source: inherited from Q90

Coder workflow for Q90.9

MedCoder structured workflow — derived from this code’s own official record

Before you code Q90.9

  1. Unspecified does not mean incorrect. When the record gives no greater specificity, Q90.9 may be the appropriate code. Check the record for detail that supports a more specific sibling. An unspecified code is for records that do not provide the detail a more specific code needs; a query, not an assumption, is the route to specificity (Guidelines I.A.9.b, I.B.18).

    ReviewQ90.0, Q90.1, Q90.2

    See the relationships section · Guide: Other vs unspecified (NEC vs NOS) →

Choose the right path

  1. Does the record document the detail a more specific sibling code needs?
    Yes → Review the specific siblings in this subcategory.
    No → Continue — Q90.9 is appropriate when the documentation goes no further.

    ReviewQ90.0, Q90.1, Q90.2

Consider Q90.9. Then work the Use Additional Code note and review the Code Also note, and confirm the code is valid for the date of service in the Verify section.

Documentation check

The provider’s diagnostic statement
Codes are assigned from the provider’s documented diagnosis, not from clinical criteria, test values or a medication list (Guidelines I.A.19).
The conditions the Use Additional Code note names
Reported with this code when documented; a conditional instruction (“if applicable”, “if known”) applies only when the record supports it.
Any detail beyond this code’s title
What the record states that a more specific sibling code would capture — or its absence, which itself supports the unspecified code.

Official instructions as workflow

  • Excludes2 — not part of Q90.9(1 note)

    Coding workflow: The conditions named in this note are not included in Q90.9. When the record documents both, both may be reported; the note is a boundary, not a prohibition.

    CompareE88.4

    See the official tabular notes · Guidelines I.A.12.b

  • Use Additional Code — after identifying Q90.9(1 note)

    Coding workflow: Check whether the documentation supports the additional code(s) the note names, and report them with Q90.9 when it does. Where the instruction is conditional (“if applicable”, “if known”), it applies only when the record documents the condition.

    See the official tabular notes · Guidelines I.A.13

  • Code Also — related condition(1 note)

    Coding workflow: Review the related condition when both are documented and the instruction applies. A Code Also note does not fix sequencing; the order follows the circumstances of the encounter.

    ReviewQ21.2

    See the official tabular notes · Guidelines I.A.17

Coding decision scenarios

Pattern scenarios for this code’s structure — decision rules, not clinical cases

Documentation: The provider documents the condition in the terms of this code’s title and records no further detail.

Coding question: Is a more specific sibling code supportable?

Path: Review the specific siblings in this subcategory and what each requires the record to state.

Reason: A more specific code needs documentation of the distinguishing element; without it the unspecified code is appropriate, and a provider query is the route to specificity (Guidelines I.A.9.b, I.B.18).

ReviewQ90.0, Q90.1, Q90.2

Documentation: A condition the Use Additional Code note names is documented.

Coding question: Is a second code reported with Q90.9?

Path: Review the Use Additional Code note and the code it names.

Reason: The additional code is reported when the record documents the condition; a conditional instruction applies only when its condition is met (Guidelines I.A.13).

Every row is derived from this code’s own record — its title, tabular notes, 7th-character family and same-category siblings — with fixed MedCoder wording; nothing is inferred about a patient. The official notes and guideline text are in the sections each row links to, and they control.

Code Overview

Down syndrome, unspecified is a billable ICD-10-CM diagnosis code (Q90.9).

MedCoder summary Summary composed by MedCoder from this code's official ICD-10-CM record. The tabular instructional notes themselves appear verbatim below.

Indexed Clinical Terms (4)

Official source data — entries quoted as published, in the Index’s own lookup phrasing

Clinical term phrases from the official ICD-10-CM Index to Diseases and Injuries that map to this code. These are alphabetic-index entries shown as the Index writes them — lookup phrasing, not necessarily the wording of a final diagnosis.

Decision Points

The directives on this code's own record, as a pre-claim checklist.

  1. 1 Use Additional Code instruction — report the named additional code(s) when the documentation supports them. See the Use Additional Code notes
  2. 1 Code Also note — a second code may apply; the guidelines leave its sequencing to the circumstances of the encounter. See the Code Also notes
  3. 1 Excludes2 entry — those conditions are not part of this code and may be reported additionally when documented. See the Excludes2 notes

Checklist rows are derived from this code's own official directives; the wording of each check is MedCoder editorial. The official notes themselves are in the sections each row links to.

Verify Before Coding

  • No Medicare Code Editor or MS-DRG Definitions Manual restrictions apply to this code.

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

MedCoder structured relationships — computed from published CMS and AHRQ datasets

Other codes that name Q90.9 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 11 Excludes1 notes across 3 chapters: E25 — Adrenogenital disorders (via Q90.-), Q50 — Congenital malformations of ovaries, fallopian tubes and broad ligaments (via Q90.-), Q50-Q56 — Congenital malformations of genital organs (Q50-Q56) (via Q90.-), Q51 — Congenital malformations of uterus and cervix (via Q90.-), Q52 — Other congenital malformations of female genitalia (via Q90.-), Q53 — Undescended and ectopic testicle (via Q90.-), Q54 — Hypospadias (via Q90.-), Q55 — Other congenital malformations of male genital organs (via Q90.-), Q56 — Indeterminate sex and pseudohermaphroditism (via Q90.-), Q92 — Other trisomies and partial trisomies of the autosomes, not elsewhere classified (via Q90.-), Z15 — Genetic susceptibility to disease (via Q90.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Referenced by 1 Code First instruction: D84.81 — Immunodeficiency due to conditions classified elsewhere (via Q90.-).

Each of these codes carries a Code First note naming this condition — when that code is reported, THIS code is sequenced first, ahead of it.

MS-DRG Grouper Relationships (FY2026)

Potential MS-DRG participation — not a DRG assignment.

FY2026 MS-DRG: not on the CMS CC/MCC list — as a secondary diagnosis this code does not change MS-DRG severity for that release.

Named in the grouper logic of 1 MS-DRG: DRG 884 (MDC 19).

From the CMS MS-DRG Definitions Manual (Appendices B and C). Actual DRG assignment depends on the complete claim.

Clinical classification (AHRQ CCSR):MAL009 — Chromosomal abnormalities (default).

Clinical Classifications Software Refined (CCSR) for ICD-10-CM Diagnoses. Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality.

Related Codes

Same clinical category (CCSR)

AHRQ's Clinical Classifications Software groups these diagnoses under the same clinical category (Chromosomal abnormalities).

Q87.86 — Kleefstra syndrome, Q90.0 — Trisomy 21, nonmosaicism (meiotic nondisjunction), Q90.1 — Trisomy 21, mosaicism (mitotic nondisjunction), Q90.2 — Trisomy 21, translocation, Q91.0 — Trisomy 18, nonmosaicism (meiotic nondisjunction), Q91.1 — Trisomy 18, mosaicism (mitotic nondisjunction), Q91.2 — Trisomy 18, translocation, Q91.3 — Trisomy 18, unspecified, Q91.4 — Trisomy 13, nonmosaicism (meiotic nondisjunction), Q91.5 — Trisomy 13, mosaicism (mitotic nondisjunction), Q91.6 — Trisomy 13, translocation, Q91.7 — Trisomy 13, unspecified, Q92.0 — Whole chromosome trisomy, nonmosaicism (meiotic nondisjunction), Q92.1 — Whole chromosome trisomy, mosaicism (mitotic nondisjunction), Q92.2 — Partial trisomy, Q92.5 — Duplications with other complex rearrangements, Q92.61 — Marker chromosomes in normal individual, Q92.62 — Marker chromosomes in abnormal individual, Q92.7 — Triploidy and polyploidy, Q92.8 — Other specified trisomies and partial trisomies of autosomes, +56 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main term “Trisomy”; these codes share that main term but sit in a different category of the Tabular List.

Q91.0 — Trisomy 18, nonmosaicism (meiotic nondisjunction) (18, meiotic nondisjunction), Q91.1 — Trisomy 18, mosaicism (mitotic nondisjunction) (18, mosaicism), Q91.2 — Trisomy 18, translocation (18, translocation), Q91.3 — Trisomy 18, unspecified (18), Q91.4 — Trisomy 13, nonmosaicism (meiotic nondisjunction) (13, meiotic nondisjunction), Q91.5 — Trisomy 13, mosaicism (mitotic nondisjunction) (13, mosaicism), Q91.6 — Trisomy 13, translocation (13, translocation), Q91.7 — Trisomy 13, unspecified (13), Q92.0 — Whole chromosome trisomy, nonmosaicism (meiotic nondisjunction) (whole chromosome, meiotic nondisjunction), Q92.1 — Whole chromosome trisomy, mosaicism (mitotic nondisjunction) (whole chromosome, mosaicism), Q92.2 — Partial trisomy (chromosome specified NEC, partial), Q92.5 — Duplications with other complex rearrangements (chromosome specified NEC, partial, due to unbalanced translocation), Q92.8 — Other specified trisomies and partial trisomies of autosomes (20), Q92.9 — Trisomy and partial trisomy of autosomes, unspecified

Contextual Map

Every relationship of Q90.9 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Run Q90.9 with these 9 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes (11)

Referenced by Code First instructions

Clinical classification (CCSR)

MS-DRG Grouper

MDC crossing

  • MDC 19 — Mental Diseases and Disorders[MDC crossing]: “Mental Diseases and Disorders — the grouper's crossing between diagnoses and procedures: a principal diagnosis sets the MDC, and same-MDC procedures move the stay to its surgical DRGs.”— CMS MS-DRG Definitions Manual · FY2026

Index entries

  • Down syndrome[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, Down[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, trisomy, 21[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Trisomy (syndrome), 21 (partial)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes

Change history

  • FY2016 — In the code set at ICD-10-CM adoption [Change history]— CMS release files (code change ledger) · icd10cm-fy2016

Sources for this page

Codes, titles, notes, index terms and mappings on this page are transcribed from the datasets below. Relationships MedCoder computed and text MedCoder wrote are labelled where they appear.

Code, title, tabular notes and index terms Official source data
CMS/CDC ICD-10-CM FY2026 tabular list, index and tables, effective October 1, 2025 Release, file and checksum · Publisher’s page
Claim edits Official source data
CMS Definitions of Medicare Code Edits — v43.1 (April 2026) Release, file and checksum · Publisher’s page
Inpatient payment groups Official source data
CMS MS-DRG Definitions Manual (incl. Appendix B diagnosis index, Appendix C CC/MCC list, Appendix E procedure index) and IPPS Final Rule tables — v43 Release, file and checksum · Publisher’s page
Change history and date-of-service validity Official source data
CMS ICD-10-CM release addenda, ingested release by release into the change ledger Release, file and checksum · Publisher’s page
Comparisons, relationships and the contextual map MedCoder structured relationship
Computed by MedCoder from the tabular notes and tables above; every derived relationship is marked as derived where it appears
Summary and FAQ answers MedCoder explanation
Written by MedCoder to explain the sources above: drafted with AI assistance, checked by a person against the release files, and labelled as MedCoder text where it appears. Not official text.

Labels on this page: Official source data · MedCoder structured relationship · MedCoder explanation. How to read the labels · All data sources and release dates

Cite this page

Reference this page in a research guide, syllabus or article. The release is included because code content changes each year.

MedCoder.ai. "Q90.9 — Down syndrome, unspecified." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/q90.9-down-syndrome-unspecified

Change history

  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Down syndrome, unspecified

No changes since FY2016 — additions, deletions, description changes and billable-status changes are tracked through FY2027 (effective October 1, 2026), and none are recorded for this code. Note changes are tracked from FY2027 only.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Q90.9 in its code family, with their registry titles.

View all codes in the Q90 family