2027 ICD-10-CM Diagnosis Code Q99Other chromosome abnormalities, not elsewhere classified

ICD-10-CM Codes›Q00-Q99›Q90-Q99›Q99

ICD-10-CM Q99
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

Q99 is a non-billable ICD-10-CM category code for other chromosome abnormalities, not elsewhere classified, so it cannot be submitted on claims. Use a more specific code from this category instead, such as Q99.0, Q99.1, Q99.2, and Q99.811.

Code Identity

ICD-10-CM Code
Q99
Billable Status
No — Non-Billable Category
Code Describes
Other chromosome abnormalities, not elsewhere classified
Short Description
Other chromosome abnormalities, not elsewhere classified
Same as the full description in the CMS dataset.
Chapter
Q90-Q99
Chromosomal abnormalities, not elsewhere classified

Code Classification

ChapterQ00-Q99Congenital malformations, deformations and chromosomal abnormalities
SectionQ90-Q99Chromosomal abnormalities, not elsewhere classified
CategoryQ99Other chromosome abnormalities, not elsewhere classified
This CodeQ99Other chromosome abnormalities, not elsewhere classified

Specific Coding for Other chromosome abnormalities, not elsewhere classifiedOverview

Non-specific codes like Q99 require more characters. Use one of these billable codes instead:

  • Use Q99.0 for Chimera 46, XX/46, XY

  • Use Q99.1 for 46, XX true hermaphrodite

  • Use Q99.2 for Fragile X chromosome

  • Q99.8 for Other specified chromosome abnormalities

  • Q99.81 for Usher syndrome

  • Use Q99.89 for Other specified chromosome abnormalities

  • Use Q99.9 for Chromosomal abnormality, unspecified

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to Q99: its own notes plus those printed at block Q90-Q99 and Chapter 17. A note printed at a category, block or chapter applies to every code under it.

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Block Q90-Q99 Chromosomal abnormalities, not elsewhere classified applies to 74 codes
  • mitochondrial metabolic disorders (E88.4-)
From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • inborn errors of metabolism (E70-E88)

Notes

General instructions on how these codes are used.

From Chapter 17 (Q00-QA1) Congenital malformations, deformations and chromosomal abnormalities applies to 900 codes
  • Codes from this chapter are not for use on maternal records

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name Q99, its category, or a range that includes it.

Excludes1 4

These codes carry an Excludes1 note naming Q99: they are not reported together with it, unless the two conditions are unrelated.

  • E25 Adrenogenital disorders
    chromosomal abnormalities (Q90-Q99) names Q90-Q99, which includes this code
  • Block Q50-Q56 Congenital malformations of genital organs
    syndromes associated with anomalies in the number and form of chromosomes (Q90-Q99) names Q90-Q99, which includes this code
  • Q56 Indeterminate sex and pseudohermaphroditism
    pseudohermaphroditism with specified chromosomal anomaly (Q96-Q99) names Q96-Q99, which includes this code
  • Z15 Genetic susceptibility to disease
    chromosomal anomalies (Q90-Q99) names Q90-Q99, which includes this code

Code First 1

These codes say to code first a condition named in the note, and Q99 is one of the conditions named.

  • D84.81 Immunodeficiency due to conditions classified elsewhere
    chromosomal abnormalities (Q90-Q99) names Q90-Q99, which includes this code

Patient EducationClinical

Genetic Disorders

Genetic disorders are health conditions caused by changes (also called mutations or variants) in your genes. Genes are parts of DNA found in your cells that carry instructions for how your body grows, develops, and functions. Many genes tell your body how to make proteins, which are needed for your body to work properly.

The full article covers:

  • What are genetic disorders?
  • What causes genetic disorders?
  • What are the types of genetic disorders?
  • What are the different ways a genetic disorder can be inherited?
  • How are genetic disorders diagnosed?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About Q99Overview

What is the ICD-10 code for other chromosome abnormalities, not elsewhere classified?

Q99 is the ICD-10-CM category for other chromosome abnormalities, not elsewhere classified, but it is a non-billable header: claims need a more specific code from this category, listed on this page.

Is Q99 (Other chromosome abnormalities, not elsewhere classified) a billable code?

No. This is a category header that groups the codes for other chromosome abnormalities, not elsewhere classified, and headers cannot be submitted on claims. Claims for other chromosome abnormalities, not elsewhere classified need a more specific code from this category, such as Q99.0, Q99.1, and Q99.2.