2026 ICD-10-CM Diagnosis Code Q99.2Fragile X chromosome

ICD-10-CM Codes›Q00-Q99›Q90-Q99›Q99

ICD-10-CM Q99.2
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

Q99.2 is a billable ICD-10-CM diagnosis code for fragile X chromosome. 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
Q99.2
Billable Status
Yes — Valid for Submission
Code Describes
Fragile X chromosome
Short Description
Fragile X chromosome
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 CodeQ99.2Fragile X chromosome

Present on Admission (POA)Billing

Q99.2 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.

  • Dementia due to chromosomal anomaly
  • Dementia due to fragile X syndrome
  • Dementia due to genetic disease
  • Fragile X associated primary ovarian insufficiency
  • Fragile X associated tremor ataxia syndrome
  • Fragile X chromosome
  • Fragile X syndrome
  • FRAXE intellectual disability syndrome
  • FRAXF syndrome
  • Premature ovarian failure

Tabular List NotesGuidance

Coding notes and annotation back-references applicable to this code.

Inclusion Terms

  • Fragile X 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.

    • Fragile, fragility
      • X chromosome
    • Syndrome
      • fragile X

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

  • Fragile X Syndrome

    a condition characterized genotypically by mutation of the distal end of the long arm of the x chromosome (at gene loci fraxa or fraxe) and phenotypically by cognitive impairment, hyperactivity, seizures, language delay, and enlargement of the ears, head, and testes. intellectual disability occurs in nearly all males and roughly 50% of females with the full mutation of fraxa. (from menkes, textbook of child neurology, 5th ed, p226)

  • Fragile X Syndrome

    a genetic syndrome caused by mutations in the fmr1 gene which is responsible for the expression of the fragile x mental retardation 1 protein. this protein participates in neural development. this syndrome is manifested with mental, emotional, behavioral, physical, and learning disabilities.

Patient EducationClinical

Fragile X Syndrome

Fragile X syndrome is the most common form of inherited developmental disability. A problem with a specific gene causes the disease. Normally, the gene makes a protein you need for brain development. But the problem causes a person to make little or none of the protein. This causes the symptoms of Fragile X.

Read the full article at MedlinePlus

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

Convert Q99.2 to ICD-9-CMHistory

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

ICD-9-CM
759.83 Fragile x syndrome
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 Q99.2Overview

Is Q99.2 (Other chromosome abnormalities, not elsewhere classified) a billable code?

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

Is Q99.2 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 fragile X chromosome on inpatient claims.

What is the ICD-9 equivalent of Q99.2?

Under the General Equivalence Mappings, fragile X chromosome converts to ICD-9-CM 759.83 (fragile x syndrome). 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.