A56 vs P23.1
A56 and P23.1 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 A56
neonatal chlamydial pneumonia (P23.1)
A56
Other sexually transmitted chlamydial diseases
Not billable
- Chapter 1
- Certain infectious and parasitic diseases
- Section
- A50-A64
Use when the record says
- sexually transmitted diseases due to Chlamydia
- trachomatis
P23.1
Congenital pneumonia due to Chlamydia
Billable
- Chapter 16
- Certain conditions originating in the perinatal period
- Section
- P19-P29
Indexed under
- Pneumonia › chlamydial › congenital (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Pneumonia › congenital › due to › Chlamydia (acute) (double) (migratory) (purulent) (septic) (unresolved)
- Pneumonia › in › Chlamydia › neonatal (acute) (double) (migratory) (purulent) (septic) (unresolved)
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