FY2027
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Excludes1 pair

G20.C vs G21-

G20.C and G21 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 G20.C
secondary parkinsonism (G21.-)
G20.C

Parkinsonism, unspecified

BillableUnspecified
Chapter 6
Diseases of the nervous system
Section
G20-G26
Use when the record says
  • Parkinsonism, NOS
Indexed under
  • Hemiparkinsonism
  • Parkinsonism (idiopathic) (primary)
  • Pyramidopallidonigral syndrome
  • Paralysis, paralytic › agitans
  • Parkinsonism › dementia
G21

Secondary parkinsonism

Not billable
Chapter 6
Diseases of the nervous system
Section
G20-G26

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