Trisomy 18 and Trisomy 13 (Q91) ICD-10-CM
The Q91 code range covers trisomy 18 and trisomy 13 with 9 ICD-10-CM diagnosis codes. 8 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Codes in the Q91 Range 9 codes · 8 billable
- Q91 Trisomy 18 and Trisomy 13Non-billable
- Q91.0 Trisomy 18, nonmosaicism (meiotic nondisjunction)
- Q91.1 Trisomy 18, mosaicism (mitotic nondisjunction)
- Q91.2 Trisomy 18, translocation
- Q91.3 Trisomy 18, unspecified
- Q91.4 Trisomy 13, nonmosaicism (meiotic nondisjunction)
- Q91.5 Trisomy 13, mosaicism (mitotic nondisjunction)
- Q91.6 Trisomy 13, translocation
- Q91.7 Trisomy 13, unspecified
About the Q91 Code Range
ICD-10 codes Q91 cover genetic chromosomal abnormalities known as Trisomy 18 and Trisomy 13, including their various forms such as nonmosaicism, mosaicism, and translocation types. These codes are used specifically to identify and classify different presentations of these serious congenital conditions.
The code Q91 and its subcategories relate to Trisomy 18—also called Edward’s syndrome—and Trisomy 13, known as Patau’s syndrome. These syndromes occur when an individual has an extra copy of chromosome 18 or 13, respectively. The set includes distinctions such as Q91.0 and Q91.4, identifying nonmosaicism cases due to meiotic nondisjunction (complete extra chromosome), and Q91.1 and Q91.5 for mosaicism from mitotic nondisjunction, where only some cells have the extra chromosome. Translocation forms, coded as Q91.2 and Q91.6, indicate partial trisomies caused by chromosome rearrangement. Unspecified cases fall under Q91.3 and Q91.7. Recognizing these synonyms and variants, such as "Complete trisomy 18 syndrome" or "Partial trisomy 13 in Patau's syndrome," helps medical coders accurately assign the correct ICD-10 code based on precise clinical and genetic findings. This section is essential for diagnosing, documenting, and billing genetic testing and related healthcare services for these complex chromosomal disorders.
Questions About This Page
How many billable codes are in the Q91 range?
Of the 9 codes in this range, 8 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the Q91 range classify?
The range classifies trisomy 18 and trisomy 13. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
