ICD-10-CM 2027
ICD-10 code for cytomegaloviral mononucleosis
From the official ICD-10-CM alphabetic index entry “Mononucleosis, infectious › cytomegaloviral”. Page updated September 29, 2026.
About coding cytomegaloviral mononucleosis
The ICD-10-CM code for cytomegaloviral mononucleosis is B27.10 (Cytomegaloviral mononucleosis without complications). The official index lists 3 more specific codes, so check the documentation for details such as type, cause, site or severity before settling on B27.10.
Within B27.1, choose B27.10 (without complications) only when documentation doesn't support a more specific option: with polyneuropathy (B27.11), with meningitis (B27.12) and with other complication (B27.19).
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.
More specific cytomegaloviral mononucleosis codes (official index)
Common questions about cytomegaloviral mononucleosis ICD-10 codes
What is the ICD-10 code for cytomegaloviral mononucleosis?
- B27.10 — Cytomegaloviral mononucleosis without complications. More specific codes apply when the documentation supports them: B27.19, B27.12, B27.11.
Is B27.10 billable?
- Yes. B27.10 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can B27.10 be used as a principal diagnosis?
- Yes. The Medicare Code Editor doesn't restrict B27.10 as a principal diagnosis.
Is B27.10 a CC or MCC?
- No. B27.10 is neither a CC nor an MCC under MS-DRG v44.0.