B27 vs D72.821
B27 (Infectious mononucleosis) compared with D72.821 (Monocytosis (symptomatic)), from the official CMS tabular data. Do not report these codes together: the official tabular list marks them Excludes1.
Can these codes be reported together?
No — do not report together. D72.821 carries an Excludes1 note covering B27: “infectious mononucleosis (B27.-)”
Sole exception: when the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).
Side by side
| B27Infectious mononucleosis | D72.821Monocytosis (symptomatic) | |
|---|---|---|
| Billing status | Non-billable header | Billable |
| Classification | A00-B99 — Certain Infectious and Parasitic Diseases (A00-B99) | D50-D89 — Diseases of the Blood and Blood-forming Organs and Certain Disorders Involving the Immune Mechanism (D50-D89) |
| Definition | Infectious mononucleosis is a non-billable ICD-10-CM category code (B27). | Monocytosis (symptomatic) is a billable ICD-10-CM diagnosis code (D72.821). |
| Includes | glandular fever monocytic angina Pfeiffer's disease | — |
Derived from the official CMS ICD-10-CM tabular data (FY2026). Not billing advice; verify sequencing rules for the encounter. All data sources