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Q99.8 ICD-10-CM Code: Other specified chromosome abnormalities

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Coding at a Glance

Tabular directives
1 Excludes2

Coding instructions

Official Tabular Instructional Notes: the inclusion, exclusion and sequencing notes published for Q99.8 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 Q99.8 itself; “inherited from” names the category or block whose note applies here.

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

Coder workflow for Q99.8

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

Before you code Q99.8

  1. Q99.8 is not reportable as written. Select the more specific code beneath it that the documentation supports. Codes are reported to the highest level of specificity the classification provides (Guidelines I.B.2).

    ReviewQ99.81, Q99.89

    See the relationships section · Guide: How to choose an ICD-10-CM code →

  2. “Other” (NEC) means the condition is specified in the record but no dedicated code captures it. Confirm the documented form is not one a sibling code names before settling on Q99.8; if the record states no specifics at all, the unspecified sibling applies instead. “Other” codes are for documented conditions the classification gives no specific code; “unspecified” codes are for records lacking the detail (Guidelines I.A.9.a, I.A.9.b).

    ReviewQ99.0, Q99.1, Q99.2

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

Choose the right path

  1. Does the documentation support one of the more specific codes beneath Q99.8?
    Yes → Select that code and continue the checks below on its own page.
    No → Q99.8 cannot be reported as written; query for the specificity its subcategory needs.

    ReviewQ99.81, Q99.89

Consider Q99.8. Then 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).
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 Q99.8(1 note)

    Coding workflow: The conditions named in this note are not included in Q99.8. 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

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

Other specified chromosome abnormalities is a non-billable ICD-10-CM category code (Q99.8). A more specific billable subcode must be selected for claims submission.

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 (6)

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.

Verify Before Coding

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 Q99.8 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 10 Excludes1 notes across 3 chapters: E25 — Adrenogenital disorders (via Q99.-), Q50 — Congenital malformations of ovaries, fallopian tubes and broad ligaments (via Q99.-), Q50-Q56 — Congenital malformations of genital organs (Q50-Q56) (via Q99.-), Q51 — Congenital malformations of uterus and cervix (via Q99.-), Q52 — Other congenital malformations of female genitalia (via Q99.-), Q53 — Undescended and ectopic testicle (via Q99.-), Q54 — Hypospadias (via Q99.-), Q55 — Other congenital malformations of male genital organs (via Q99.-), Q56 — Indeterminate sex and pseudohermaphroditism (via Q99.-), Z15 — Genetic susceptibility to disease (via Q99.-).

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 Q99.-).

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.

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).

Q97.9 — Sex chromosome abnormality, female phenotype, unspecified, Q98.0 — Klinefelter syndrome karyotype 47, XXY, Q98.1 — Klinefelter syndrome, male with more than two X chromosomes, Q98.3 — Other male with 46, XX karyotype, Q98.4 — Klinefelter syndrome, unspecified, Q98.5 — Karyotype 47, XYY, Q98.6 — Male with structurally abnormal sex chromosome, Q98.7 — Male with sex chromosome mosaicism, Q98.8 — Other specified sex chromosome abnormalities, male phenotype, Q98.9 — Sex chromosome abnormality, male phenotype, unspecified, Q99.0 — Chimera 46, XX/46, XY, Q99.1 — 46, XX true hermaphrodite, Q99.2 — Fragile X chromosome, Q99.811 — Usher syndrome, type 1, Q99.812 — Usher syndrome, type 2, Q99.813 — Usher syndrome, type 3, Q99.818 — Other Usher syndrome, Q99.819 — Usher syndrome, unspecified, Q99.89 — Other specified chromosome abnormalities, Q99.9 — Chromosomal abnormality, unspecified, +56 more

Same Index main term, other category

The ICD-10-CM Index to Diseases and Injuries files this code under the main terms “Abnormal, abnormality, abnormalities”, “Anomaly, anomalous”, “Translocation”; these codes share that main term but sit in a different category of the Tabular List.

Q95.5 — Individual with autosomal fragile site (autosomes, fragile site), Q95.9 — Balanced rearrangement and structural marker, unspecified (balanced autosomal), Q96.9 — Turner's syndrome, unspecified (chromosomes, chromosomal, sex, Turner's), Q97.1 — Female with more than three X chromosomes (chromosome, chromosomal, with more than three X chromosomes, female), Q97.8 — Other specified sex chromosome abnormalities, female phenotype (sex chromosomes NEC, female phenotype), Q97.9 — Sex chromosome abnormality, female phenotype, unspecified (chromosome, chromosomal, sex, female phenotype), Q98.4 — Klinefelter syndrome, unspecified (chromosomes, chromosomal, sex, Klinefelter's), Q98.6 — Male with structurally abnormal sex chromosome (chromosome, chromosomal, sex, structural male), Q98.8 — Other specified sex chromosome abnormalities, male phenotype (chromosome, chromosomal, sex, male phenotype, specified NEC), Q98.9 — Sex chromosome abnormality, male phenotype, unspecified (sex chromosomes NEC, male phenotype), R00.2 — Palpitations (pulsations in neck), R00.8 — Other abnormalities of heart beat (heart, rate, specified NEC), R00.9 — Unspecified abnormalities of heart beat (heart, rate), R01.2 — Other cardiac sounds (heart, sounds NEC), R03.0 — Elevated blood-pressure reading, without diagnosis of hypertension (blood pressure, elevated), R03.1 — Nonspecific low blood-pressure reading (blood pressure, low reading), R06.9 — Unspecified abnormalities of breathing (breathing), R09.3 — Abnormal sputum (sputum), R09.89 — Other specified symptoms and signs involving the circulatory and respiratory systems (chest sounds), R19.11 — Absent bowel sounds (bowel sounds, absent), +483 more

Contextual Map

Every relationship of Q99.8 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 Q99.8 with these 9 related codes in Claim Check

Hierarchy

Referenced by Excludes1 notes (10)

Referenced by Code First instructions

Clinical classification (CCSR)

Index entries

  • Abnormal, abnormality, abnormalities, chromosome, chromosomal, sex[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Abnormal, abnormality, abnormalities, chromosome, chromosomal, specified NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Additional, chromosome (s)[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Anomaly, anomalous (congenital) (unspecified type), chromosomes, chromosomal, specified NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Syndrome, due to abnormality, chromosomal, specified NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026
  • Translocation, chromosomes NEC[Index term]— CMS ICD-10-CM Index to Diseases and Injuries · icd10cm-fy2026

Nearest codes (12)

Change history (2)

Common coding questions

Can Q99.8 be billed directly?

No. Q99.8 (Other specified chromosome abnormalities) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

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
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. "Q99.8 — Other specified chromosome abnormalities." ICD-10-CM FY2026. https://medcoder.ai/icd10/code/q99.8-other-specified-chromosome-abnormalities

Change history

  • FY2026 — October 1, 2025
    Became a non-billable header
    FY2026 changes
  • FY2016 — October 1, 2015
    In the code set at ICD-10-CM adoption
    Other specified chromosome abnormalities

Nearest Codes in This Family

Official ICD-10-CM classifications closest to Q99.8 in its code family, with their registry titles.

View all codes in the Q99 family