B27 vs G02
B27 and G02 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on G02
infectious mononucleosis complicated by meningitis (B27.- with fifth character 2)
B27
Infectious mononucleosis
Not billable
- Chapter 1
- Certain infectious and parasitic diseases
- Section
- B25-B34
Use when the record says
- glandular fever
- monocytic angina
- Pfeiffer's disease
G02
Meningitis in other infectious and parasitic diseases classified elsewhere
Billable
- Chapter 6
- Diseases of the nervous system
- Section
- G00-G09
Indexed under
- Exanthem, exanthema › epidemic with meningitis
- Meningitis › mycotic NEC (basal) (basic) (brain) (cerebral) (cervical) (congestive) (diffuse) (hemorrhagic) (infantile) (membranous) (metastatic) (nonspecific) (pontine) (progressive) (simple) (spinal) (subacute) (sympathetic) (toxic)
- Meningitis › poliovirus (basal) (basic) (brain) (cerebral) (cervical) (congestive) (diffuse) (hemorrhagic) (infantile) (membranous) (metastatic) (nonspecific) (pontine) (progressive) (simple) (spinal) (subacute) (sympathetic) (toxic)
- Meningitis › in › African trypanosomiasis (basal) (basic) (brain) (cerebral) (cervical) (congestive) (diffuse) (hemorrhagic) (infantile) (membranous) (metastatic) (nonspecific) (pontine) (progressive) (simple) (spinal) (subacute) (sympathetic) (toxic)
- Meningitis › in › parasitic disease NEC (basal) (basic) (brain) (cerebral) (cervical) (congestive) (diffuse) (hemorrhagic) (infantile) (membranous) (metastatic) (nonspecific) (pontine) (progressive) (simple) (spinal) (subacute) (sympathetic) (toxic)
These two codes sit in different chapters of the Tabular List, which is usually the clearest signal that they describe different underlying processes rather than different degrees of the same one.
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027