2026 ICD-10-CM Diagnosis Code Q99.9Chromosomal abnormality, unspecified

ICD-10-CM Codes›Q00-Q99›Q90-Q99›Q99

ICD-10-CM Q99.9
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q99.9 is a billable ICD-10-CM diagnosis code for chromosomal abnormality, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Chromosomal abnormalities.

Code Identity

ICD-10-CM Code
Q99.9
Billable Status
Yes — Valid for Submission
Code Describes
Chromosomal abnormality, unspecified
Short Description
Chromosomal abnormality, unspecified
Same as the full description in the CMS dataset.
Parent Code
Q99
Other chromosome 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 CodeQ99.9Chromosomal abnormality, unspecified

Present on Admission (POA)Billing

Q99.9 is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Alpha-thalassemia intellectual disability syndrome linked to chromosome 16
  • Anomaly of chromosome pair 1
  • Anomaly of chromosome pair 10
  • Anomaly of chromosome pair 11
  • Anomaly of chromosome pair 12
  • Anomaly of chromosome pair 13
  • Anomaly of chromosome pair 14
  • Anomaly of chromosome pair 15
  • Anomaly of chromosome pair 16
  • Anomaly of chromosome pair 17
  • Anomaly of chromosome pair 18
  • Anomaly of chromosome pair 19
  • Anomaly of chromosome pair 2
  • Anomaly of chromosome pair 20
  • Anomaly of chromosome pair 21
  • Anomaly of chromosome pair 22
  • Anomaly of chromosome pair 3
  • Anomaly of chromosome pair 4
  • Anomaly of chromosome pair 5
  • Anomaly of chromosome pair 6
  • Anomaly of chromosome pair 7
  • Anomaly of chromosome pair 8
  • Anomaly of chromosome pair 9
  • Autoimmune lymphoproliferative syndrome
  • Autoimmune lymphoproliferative syndrome due to CTLA4 haploinsufficiency
  • Autosomal chromosomal disorder
  • Autosomal dominant hereditary disorder
  • Autosomal hereditary disorder
  • Autosomal recessive hereditary disorder
  • Autosomal translocation
  • Cardiac arrhythmia associated with genetic disorder
  • CFTR-related disorder
  • Chromosomal disorder
  • Congenital chromosomal disease
  • Deletion of part of short arm of chromosome 16
  • Dementia due to chromosomal anomaly
  • Dementia due to genetic disease
  • Dominant autosomal hereditary disorder, complete penetrance
  • Dominant autosomal hereditary disorder, incomplete penetrance
  • Genetic disease
  • Immunodeficiency associated with chromosomal abnormality
  • Ulnar mammary syndrome

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Abnormal, abnormality, abnormalities
      • autosomes
    • Abnormal, abnormality, abnormalities
      • chromosome, chromosomal
    • Anomaly, anomalous(congenital) (unspecified type)
      • chromosomes, chromosomal
    • Syndrome
      • due to abnormality
        • chromosomal

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR MAL009
Chromosomal abnormalities
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Autoimmune Lymphoproliferative Syndrome

    rare congenital lymphoid disorder due to mutations in certain fas-fas ligand pathway genes. known causes include mutations in fas, tnfsf6, nras, casp8, and casp10 proteins. clinical features include lymphadenopathy; splenomegaly; and autoimmunity.

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.

Convert Q99.9 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
758.9 Chromosome anomaly NOS
Exact Match The mapping is direct, with no qualifiers.

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 Q99.9Overview

Is Q99.9 (Other chromosome abnormalities, not elsewhere classified) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report chromosomal abnormality, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

Is Q99.9 exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for chromosomal abnormality, unspecified on inpatient claims.

What is the ICD-9 equivalent of Q99.9?

Under the General Equivalence Mappings, chromosomal abnormality, unspecified converts to ICD-9-CM 758.9 (chromosome anomaly NOS). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.