ICD-10-CM 2027
ICD-10 code for infectious adenitis
From the official ICD-10-CM alphabetic index entry “Adenitis › infectious (acute) (epidemic)”. Page updated September 29, 2026.
About coding infectious adenitis
The ICD-10-CM code for infectious adenitis is B27.09 (Gammaherpesviral mononucleosis with other complications).
Within B27.0, choose B27.09 (with other complications) only when documentation doesn't support a more specific option: without complication (B27.00), with polyneuropathy (B27.01) and with meningitis (B27.02).
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 865 (Viral Illness with MCC, relative weight 1.3485) and DRG 866 (Viral Illness without MCC, relative weight 0.8692), in MDC 18 (Infectious and Parasitic Diseases, Systemic or Unspecified Sites), 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 infectious adenitis ICD-10 codes
What is the ICD-10 code for infectious adenitis?
- B27.09 — Gammaherpesviral mononucleosis with other complications.
Is B27.09 billable?
- Yes. B27.09 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can B27.09 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict B27.09 as a principal diagnosis.
Is B27.09 a CC or MCC?
- No. B27.09 is neither a CC nor an MCC under MS-DRG v44.0.