Excludes1 pair
R21 vs R23.8
R21 and R23.8 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 R21
vesicular eruption (R23.8)
R21
Rash and other nonspecific skin eruption
Billable
- Chapter 18
- Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
- Section
- R20-R23
Use when the record says
- rash NOS
Indexed under
- Rash (toxic)
- Eruption › skin (nonspecific)
- Rash › rose
- Rose › rash
R23.8
Other skin changes
Billable
- Chapter 18
- Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified
- Section
- R20-R23
Indexed under
- Bleb (s)
- Bulla (e)
- Hydroa
- Papule (s)
- Pimple
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