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  6. 2026 ICD-10-CM Code Q99.9

2026 ICD-10-CM Diagnosis Code Q99.9

Chromosomal abnormality, unspecified

ICD-10-CM Code:
Q99.9
ICD-10 Code for:
Chromosomal abnormality, unspecified
Is Billable?
Yes - Valid for Submission
Chronic Condition Indicator: [1]
Chronic
Code Navigator:

Q99.9 is a billable diagnosis code used to specify a medical diagnosis of chromosomal abnormality, unspecified. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2025 through September 30, 2026. The code is exempt from present on admission (POA) reporting for inpatient admissions to general acute care hospitals.

Unspecified diagnosis codes like Q99.9 are acceptable when clinical information is unknown or not available about a particular condition. Although a more specific code is preferable, unspecified codes should be used when such codes most accurately reflect what is known about a patient's condition. Specific diagnosis codes should not be used if not supported by the patient's medical record.

Code Classification

  • Congenital malformations, deformations and chromosomal abnormalities
    Q00-Q99
    • Chromosomal abnormalities, not elsewhere classified
      Q90-Q99
      • Other chromosome abnormalities, not elsewhere classified
        Q99

Approximate Synonyms

The following list of clinical terms are approximate synonyms, alternative descriptions, or common phrases that might be used by patients, healthcare providers, or medical coders to describe the same condition. These synonyms and related diagnosis terms are often used when searching for an ICD-10 code, especially when the exact medical terminology is unclear. Whether you're looking for lay terms, similar diagnosis names, or common language alternatives, this list can help guide you to the correct ICD-10 classification.

  • 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

Clinical Classification

Clinical Classifications group individual ICD-10-CM diagnosis codes into broader, clinically meaningful categories. These categories help simplify complex data by organizing related conditions under common clinical themes.

They are especially useful for data analysis, reporting, and clinical decision-making. Even when diagnosis codes differ, similar conditions can be grouped together based on their clinical relevance. Each category is assigned a unique CCSR code that represents a specific clinical concept, often tied to a body system or medical specialty.

Chromosomal abnormalities

CCSR Code: MAL009

Inpatient Default: Y - Yes, default inpatient assignment for principal diagnosis or first-listed diagnosis.

Outpatient Default: Y - Yes, default outpatient assignment for principal diagnosis or first-listed diagnosis.

Clinical Information

  • 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.

Index to Diseases and Injuries References

The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).

Index of External Cause of Injuries

References found for this diagnosis 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

Present on Admission (POA)

Q99.9 is exempt from POA reporting - The Present on Admission (POA) indicator is used for diagnosis codes included in claims involving inpatient admissions to general acute care hospitals. POA indicators must be reported to CMS on each claim to facilitate the grouping of diagnoses codes into the proper Diagnostic Related Groups (DRG). CMS publishes a listing of specific diagnosis codes that are exempt from the POA reporting requirement. Review other POA exempt codes here.

CMS POA Indicator Options and Definitions

POA Indicator: Y

Reason: Diagnosis was present at time of inpatient admission.

CMS Pays CC/MCC DRG? YES

POA Indicator: N

Reason: Diagnosis was not present at time of inpatient admission.

CMS Pays CC/MCC DRG? NO

POA Indicator: U

Reason: Documentation insufficient to determine if the condition was present at the time of inpatient admission.

CMS Pays CC/MCC DRG? NO

POA Indicator: W

Reason: Clinically undetermined - unable to clinically determine whether the condition was present at the time of inpatient admission.

CMS Pays CC/MCC DRG? YES

POA Indicator: 1

Reason: Unreported/Not used - Exempt from POA reporting.

CMS Pays CC/MCC DRG? NO

Convert Q99.9 to ICD-9-CM

Below are the ICD-9 codes that most closely match this ICD-10 code, based on the General Equivalence Mappings (GEMs). This ICD-10 to ICD-9 crosswalk tool is helpful for coders who need to reference legacy diagnosis codes for audits, historical claims, or approximate code comparisons.

Chromosome anomaly NOS

ICD-9-CM: 758.9

This is a direct match with no additional mapping qualifiers. The absence of a flag generally means the mapping is considered exact or precise. In other words, the ICD-10 code maps cleanly to the ICD-9 code without qualification, approximation, or needing multiple codes.

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Patient Education


Genetic Disorders

What are 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.

What causes genetic disorders?

A genetic disorder happens when a gene variant changes how a protein is made. The variant may cause the protein to work poorly or not be made at all. If genes don't make the right proteins, or don't make them correctly, it can lead to a genetic disorder.

Not all gene changes cause disease. Often, these changes have no effect. But sometimes, even a small change in DNA can affect how proteins are made.

Gene variants can be grouped into two main types:

  • Inherited variants (also called germline variants) are passed down from your parents. They come from egg or sperm cells.
  • Non-inherited (also called somatic variants) are not passed down from your parents. They happen during your lifetime. They may be caused by things like harmful chemicals or ultraviolet (UV) rays from the sun.

What are the types of genetic disorders?

Genetic disorders may be caused by:

  • Single gene disorders are caused by changes in one gene. Examples can include sickle cell anemia, where a change in a single gene can cause the condition, and Charcot-Marie-Tooth disease, where a variant in one of many different genes can cause the condition.
  • Chromosomal disorders are caused by missing, extra, or altered chromosomes. Chromosomes are structures that carry genes. These disorders involve changes in the number of chromosomes people have or changes in the structure of one or more chromosomes. An example is Down syndrome, which is caused by an extra copy of chromosome 21.
  • Complex (multifactorial) disorders are caused by changes in many genes. Each change alone may not cause the disease, but together they increase the risk. Lifestyle and environmental factors, such as exercise, diet, or exposure to pollutants, also play a role. Colon cancer is an example.

What are the different ways a genetic disorder can be inherited?

Some genetic conditions are passed down through families (inherited) in one of several patterns, depending on the specific gene involved.

Patterns of inheritance can include:

  • Dominant means you only need one changed gene to cause the condition.
  • Recessive means you need two changed copies of the gene (one from each parent) for the condition to occur.
  • X-linked conditions involve genes located on the X chromosome. These conditions often affect males more frequently.
  • Mitochondrial conditions are passed down by the mother.

How are genetic disorders diagnosed?

Your health care provider may check for a genetic condition based on:

  • A physical examination.
  • Your personal medical history.
  • Your family health history.
  • Laboratory tests, including genetic testing.

NIH: National Library of Medicine


[Learn More in MedlinePlus]

Code History

  • FY 2026 - No Change, effective from 10/1/2025 through 9/30/2026
  • FY 2025 - No Change, effective from 10/1/2024 through 9/30/2025
  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.

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.