Q99.9Chromosomal abnormality, unspecified

Q99.9 is the ICD-10-CM diagnosis code for chromosomal abnormality, unspecified. It belongs to category Q99 (other chromosome abnormalities, not elsewhere classified), block Q90-Q99 (chromosomal abnormalities, not elsewhere classified) and chapter 17 (congenital malformations, deformations, chromosomal abnormalities, and genetic disorders). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within Q99, choose Q99.9 (Chromosomal abnormality, unspecified) only when documentation doesn't support a more specific option: Chimera 46, XX/46, XY (Q99.0), 46, XX true hermaphrodite (Q99.1), fragile X chromosome (Q99.2) and other specified chromosome abnormalities (Q99.8).

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 951 (Other Factors Influencing Health Status, relative weight 0.5577), in MDC 23 (Factors Influencing Health Status and Other Contacts with Health Services), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It is exempt from present-on-admission (POA) reporting, so no POA indicator is required.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 758.9 (conditions due to anomaly of unspecified chromosome).