Excludes1 pair

A52- vs G99.8

A52 and G99.8 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 G99.8
syphilis (A52.1-)
A52

Late syphilis

Not billable
Chapter 1
Certain infectious and parasitic diseases
Section
A50-A64
G99.8

Other specified disorders of nervous system in diseases classified elsewhere

BillableUnspecified
Chapter 6
Diseases of the nervous system
Section
G89-G99
Indexed under
  • Neuroavitaminosis
  • Paralysis, paralytic › uremic
  • Degeneration, degenerative › nervous system › amyloid

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