Other chromosome abnormalities, not elsewhere classified (Q99) ICD-10-CM
The Q99 code range covers other chromosome abnormalities, not elsewhere classified with 13 ICD-10-CM diagnosis codes. 10 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Codes in the Q99 Range 13 codes · 10 billable
- Q99 Other chromosome abnormalities, not elsewhere classifiedNon-billable
- Q99.0 Chimera 46, XX/46, XY
- Q99.1 46, XX true hermaphrodite
- Q99.2 Fragile X chromosome
- Q99.8 Other specified chromosome abnormalitiesNon-billable
- Q99.81 Usher syndromeNon-billable
- Q99.811 Usher syndrome, type 1
- Q99.812 Usher syndrome, type 2
- Q99.813 Usher syndrome, type 3
- Q99.818 Other Usher syndrome
- Q99.819 Usher syndrome, unspecified
- Q99.89 Other specified chromosome abnormalities
- Q99.9 Chromosomal abnormality, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the Q99 range.
Chromosome Aberrations
Abnormal number or structure of chromosomes. Chromosome aberrations may result in CHROMOSOME DISORDERS.
Usher Syndromes
Autosomal recessive hereditary disorders characterized by congenital SENSORINEURAL HEARING LOSS and RETINITIS PIGMENTOSA. Genetically and symptomatically heterogeneous, clinical classes include type I, type II, and type III. Their severity, age of onset of retinitis pigmentosa and the degree of vestibular dysfunction are variable.
About the Q99 Code Range
These codes describe chromosome abnormalities that are not classified elsewhere. They include named conditions, other specified abnormalities, and an abnormality whose type is unspecified.
The first subdivisions identify particular conditions. Within Q99.8, Q99.81 separates Usher syndrome by type 1, 2, or 3, with options for another or an unspecified type. Q99.89 identifies other specified chromosome abnormalities, while Q99.9 leaves the abnormality unspecified.
FY 2027 changes: The FY 2027 ICD-10-CM update, effective October 1, 2026, deleted Q99.8.
Questions About This Page
How many billable codes are in the Q99 range?
Of the 13 codes in this range, 10 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the Q99 range classify?
The range classifies other chromosome abnormalities, not elsewhere classified. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
