DxCodebookFY2027 · Oct 1, 2026 – Sep 30, 2027

Category · FY2027

Q99 Other chromosome abnormalities, not elsewhere classified

  • Header · not billable

Q99 is not billable. The category heads 10 billable codes in FY2027, grouped under 5 subdivisions.

Index → code

  • Swyer syndrome → Q99.1
  • Chimera 46,XX/46,XY → Q99.0
  • SyndromeSwyer → Q99.1

Where it sits

  1. Chapter 17 Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA1)
  2. Q90-Q99 Chromosomal abnormalities, not elsewhere classified (Q90-Q99)
  3. Q99 Other chromosome abnormalities, not elsewhere classified
Billable codes
10
Subdivisions
5
CC / MCC codes
5 / 0
HCC V28 codes
0
New FY2027
0
Index entries
29

Codes in Q99

  1. Q99.0
    Chimera 46, XX/46, XY
    BillableExempt
    Inclusion terms 1

    Inclusion terms

    • Chimera 46, XX/46, XY true hermaphrodite
  2. Q99.1
    46, XX true hermaphrodite
    BillableExempt
    Inclusion terms 3

    Inclusion terms

    • 46, XX with streak gonads
    • 46, XY with streak gonads
    • Pure gonadal dysgenesis
  3. Q99.2
    Fragile X chromosome
    BillableExempt
    Inclusion terms 1

    Inclusion terms

    • Fragile X syndrome
  4. Q99.8
    Other specified chromosome abnormalities
    Header
  5. Q99.81
    Usher syndrome
    Header
    Use additional code 1

    Use additional code

    • code to identify any auditory and visual manifestations
  6. Q99.811
    Usher syndrome, type 1
    BillableCCExempt
  7. Q99.812
    Usher syndrome, type 2
    BillableCCExempt
  8. Q99.813
    Usher syndrome, type 3
    BillableCCExempt
  9. Q99.818
    Other Usher syndrome
    BillableCCExempt
    Inclusion terms 1

    Inclusion terms

    • Usher syndrome, type 4
  10. Q99.819
    Usher syndrome, unspecified
    BillableCCExempt
  11. Q99.89
    Other specified chromosome abnormalities
    BillableExempt
  12. Q99.9
    Chromosomal abnormality, unspecified
    BillableExempt

CC/MCC: as a secondary diagnosis, unless the principal diagnosis is on the code’s PDX exclusion list (MS-DRG v44 Appendix C; list on the code card).

Sources of each column.

Instructions

Notes that also apply

Block Q90-Q99 instructions (Excludes2 1): printed on the block page.

Chapter 17 instructions (Notes 1, Excludes2 1): printed on the chapter 17 page.

Index entries

  • Chimera 46,XX/46,XY → Q99.0
  • Swyer syndrome → Q99.1
  • Hermaphrodite, hermaphroditism (true)46,XX/46,XY → Q99.0
  • Hermaphrodite, hermaphroditism (true)chimera 46,XX/46,XY → Q99.0
  • Hermaphrodite, hermaphroditism (true)46,XX with streak gonads → Q99.1
  • Hermaphrodite, hermaphroditism (true)46,XY with streak gonads → Q99.1
  • SyndromeSwyer → Q99.1
  • Fragile, fragilityX chromosome → Q99.2
  • Syndromefragile X → Q99.2
  • Additionalchromosome(s) → Q99.8
  • Translocationchromosomes NEC → Q99.8
  • Syndromeusher → Q99.819
  • Abnormal, abnormality, abnormalitiesautosomes → Q99.9
  • Abnormal, abnormality, abnormalitieschromosome, chromosomal → Q99.9
  • Anomaly, anomalous (congenital) (unspecified type)chromosomes, chromosomal → Q99.9
  • Dysgenesisgonadal (due to chromosomal anomaly)pure → Q99.1
  • Karyotype46,XXhermaphrodite (true) → Q99.1
  • Karyotype46,XYhermaphrodite (true) → Q99.1
  • Abnormal, abnormality, abnormalitieschromosome, chromosomalsex → Q99.8
  • Abnormal, abnormality, abnormalitieschromosome, chromosomalspecified NEC → Q99.8
  • Anomaly, anomalous (congenital) (unspecified type)chromosomes, chromosomalspecified NEC → Q99.8
  • Syndromeushertype 1 → Q99.811
  • Syndromeushertype 2 → Q99.812
  • Syndromeushertype 3 → Q99.813
  • Syndromeusherspecified NEC → Q99.818
  • Syndromeushertype 4 → Q99.818
  • Syndromedue to abnormalitychromosomal → Q99.9
  • Anomaly, anomalous (congenital) (unspecified type)chromosomes, chromosomalsexgonadal dysgenesis (pure) → Q99.1
  • Syndromedue to abnormalitychromosomalspecified NEC → Q99.8

NCHS Alphabetic Index. Index first, then the Tabular List.

Hierarchy