ICD-10-CM 2027
ICD-10 code for X syndrome
From the official ICD-10-CM alphabetic index entry “Syndrome › X”. Page updated September 29, 2026.
About coding X syndrome
The ICD-10-CM code for X syndrome is I20.9 (Angina pectoris, unspecified).
Within I20, choose I20.9 (unspecified) only when documentation doesn't support a more specific option: unstable angina (I20.0), with documented spasm (I20.1), refractory angina pectoris (I20.2) and other forms of angina pectoris (I20.8).
Use an additional code to identify: exposure to environmental tobacco smoke (Z77.22), history of tobacco dependence (Z87.891), occupational exposure to environmental tobacco smoke (Z57.31), tobacco dependence (F17.-) and tobacco use (Z72.0).
It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.
Common questions about X syndrome ICD-10 codes
What is the ICD-10 code for X syndrome?
- I20.9 — Angina pectoris, unspecified.
Is I20.9 billable?
- Yes. I20.9 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can I20.9 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict I20.9 as a principal diagnosis.
Is I20.9 a CC or MCC?
- No. I20.9 is neither a CC nor an MCC under MS-DRG v44.0.