Q99: Other chromosome abnormalities, not elsewhere classified
Codes under Q99 (Other chromosome abnormalities, not elsewhere classified). A ✓ marks a billable (fully specified) code; category codes without a ✓ are not billable on their own.
| Code | Description | Billable |
|---|---|---|
| Q99.0 | Chimera 46, XX/46, XY | ✓ |
| Q99.0 | Chimera 46, XX/46, XY | ✓ |
| Q99.1 | 46, XX true hermaphrodite | ✓ |
| Q99.1 | 46, XX true hermaphrodite | ✓ |
| Q99.2 | Fragile X chromosome | ✓ |
| Q99.2 | Fragile X chromosome | ✓ |
| Q99.8 | Other specified chromosome abnormalities | — |
| Q99.8 | Other specified chromosome abnormalities | — |
| Q99.9 | Chromosomal abnormality, unspecified | ✓ |
| Q99.9 | Chromosomal abnormality, unspecified | ✓ |
| Q99.81 | Usher syndrome | — |
| Q99.81 | Usher syndrome | — |
| Q99.89 | Other specified chromosome abnormalities | ✓ |
| Q99.89 | Other specified chromosome abnormalities | ✓ |
| Q99.811 | Usher syndrome, type 1 | ✓ |
| Q99.811 | Usher syndrome, type 1 | ✓ |
| Q99.812 | Usher syndrome, type 2 | ✓ |
| Q99.812 | Usher syndrome, type 2 | ✓ |
| Q99.813 | Usher syndrome, type 3 | ✓ |
| Q99.813 | Usher syndrome, type 3 | ✓ |
| Q99.818 | Other Usher syndrome | ✓ |
| Q99.818 | Other Usher syndrome | ✓ |
| Q99.819 | Usher syndrome, unspecified | ✓ |
| Q99.819 | Usher syndrome, unspecified | ✓ |
Frequently asked questions
What is ICD-10-CM code Q99?
Q99 is an ICD-10-CM category covering Other chromosome abnormalities, not elsewhere classified. It contains 24 more specific diagnosis codes, 20 of which are billable.
Is Q99 a billable code?
No — Q99 is a category header and isn't billable on its own. Code to the highest level of specificity using one of its subcodes (for example Q99.0 — Chimera 46, XX/46, XY). 20 of the 24 codes under Q99 are billable.
What codes fall under Q99?
Q99 includes Q99.0, Q99.0, Q99.1, Q99.1, Q99.2, plus 19 more. See the full list with descriptions and billable status above.
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Informational only, not coding or medical advice. Verify against the official ICD-10-CM (FY2026) and your payer's guidelines.
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