Excludes1 pair
M08.1 vs M45-
M08.1 and M45 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 M08.1
ankylosing spondylitis in adults (M45.0-)
M08.1
Juvenile ankylosing spondylitis
Billable
- Chapter 13
- Diseases of the musculoskeletal system and connective tissue
- Section
- M05-M14
Indexed under
- Spondylitis › juvenile ankylosing (chronic)
- Spondylitis › ankylosing › juvenile
M45
Ankylosing spondylitis
Not billable
- Chapter 13
- Diseases of the musculoskeletal system and connective tissue
- Section
- M45-M49
Use when the record says
- Rheumatoid arthritis of spine
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