ICD-10-CM 2027
ICD-10 code for fragile X syndrome
From the official ICD-10-CM alphabetic index entry “Syndrome › fragile X”. Page updated September 29, 2026.
About coding fragile X syndrome
The ICD-10-CM code for fragile X syndrome is Q99.2 (Fragile X chromosome).
Within Q99 (other chromosome abnormalities, not elsewhere classified), Q99.2 is specifically for fragile X chromosome. Related codes cover Chimera 46, XX/46, XY (Q99.0), 46, XX true hermaphrodite (Q99.1), other specified chromosome abnormalities (Q99.8) and chromosomal abnormality, unspecified (Q99.9).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
In MS-DRG v44.0, it is part of the grouping logic for DRG 884 (Organic Disturbances and Intellectual Disability, relative weight 1.6001), in MDC 19 (Mental Diseases and Disorders), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.
Common questions about fragile X syndrome ICD-10 codes
What is the ICD-10 code for fragile X syndrome?
- Q99.2 — Fragile X chromosome.
Is Q99.2 billable?
- Yes. Q99.2 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Q99.2 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict Q99.2 as a principal diagnosis.
Is Q99.2 a CC or MCC?
- No. Q99.2 is neither a CC nor an MCC under MS-DRG v44.0.