2026 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 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

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
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

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 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About Q99Overview

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.