FY2027
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Excludes1 pair

G10 vs I02-

G10 and I02 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 I02
Huntington's chorea (G10)
G10

Huntington's disease

Billable
Chapter 6
Diseases of the nervous system
Section
G10-G14
Use when the record says
  • Huntington's chorea
  • Huntington's dementia
Indexed under
  • Huntington's disease or chorea
  • Chorea › hereditary
  • Chorea › Huntington's
  • Disease, diseased › Huntington's
  • Huntington's disease or chorea › with dementia
I02

Rheumatic chorea

Not billable
Chapter 9
Diseases of the circulatory system
Section
I00-I02
Use when the record says
  • Sydenham's chorea

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