FY2027 ICD-10-CM reference
Q99: Other chromosome abnormalities, not elsewhere classified
By the HCC Buddy Coding Team
The official ICD-10-CM descriptor is Other chromosome abnormalities, not elsewhere classified. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Nonbillable heading. Verified against the official FY2027 order file.
More specific FY2027 codes
- Q99.0: Chimera 46, XX/46, XYBillable code
- Q99.1: 46, XX true hermaphroditeBillable code
- Q99.2: Fragile X chromosomeBillable code
- Q99.8: Other specified chromosome abnormalitiesNonbillable heading
- Q99.9: Chromosomal abnormality, unspecifiedBillable code
FY2027 Tabular instructions
Instructions below include applicable chapter, section and parent-code notes. Each note identifies where it appears in the official source.
Instructional note
Codes from this chapter are not for use on maternal records
Source: Q00-QA1 (chapter, inherited).
Excludes2
inborn errors of metabolism (E70-E88)
Source: Q00-QA1 (chapter, inherited).
Excludes2
mitochondrial metabolic disorders (E88.4-)
Source: Q90-Q99 (section, inherited).
Compare the FY2027 additions, removals and billable-status changes
What does Q99 mean in FY2027?
The official ICD-10-CM descriptor is Other chromosome abnormalities, not elsewhere classified. The FY2027 annual edition starts October 1, 2026. Check the edition that applies to the encounter or inpatient discharge, including any April update.
Is Q99 billable in FY2027?
The FY2027 order file marks Q99 as a nonbillable heading. Select a complete billable child code.
Does Q99 map to an HCC?
Risk-model mapping is not applicable to this nonbillable heading. Check a complete billable child code.
Source: CMS FY2027 ICD-10-CM order file. Payment model: CMS CY 2027 Rate Announcement. Read the FY2027 Official Guidelines.
Review the FY2026 April edition