FY2027
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Excludes1 pair

A56- vs P39.1

A56 and P39.1 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 A56
neonatal chlamydial conjunctivitis (P39.1)
A56

Other sexually transmitted chlamydial diseases

Not billable
Chapter 1
Certain infectious and parasitic diseases
Section
A50-A64
Use when the record says
  • sexually transmitted diseases due to Chlamydia
  • trachomatis
P39.1

Neonatal conjunctivitis and dacryocystitis

Billable
Chapter 16
Certain conditions originating in the perinatal period
Section
P35-P39
Use when the record says
  • Neonatal chlamydial conjunctivitis
  • Ophthalmia neonatorum NOS
Indexed under
  • Blennorrhea › inclusion (neonatal) (newborn)
  • Conjunctivitis NOS › infantile
  • Conjunctivitis NOS › neonatal
  • Dacryocystitis › neonatal
  • Inclusion › blennorrhea (neonatal) (newborn)

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