Excludes1 pair
L12- vs L40.1
L12 and L40.1 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
The official note, declared on L12
impetigo herpetiformis (L40.1)
L40.1
Generalized pustular psoriasis
Billable
- Chapter 12
- Diseases of the skin and subcutaneous tissue
- Section
- L40-L45
Use when the record says
- Impetigo herpetiformis
- Von Zumbusch's disease
Indexed under
- Von Zumbusch's disease
- Impetigo › herpetiformis
- Psoriasis › pustular (generalized)
- Impetigo › herpetiformis › nonobstetrical
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