FY2027
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Excludes1 pair

I34.1 vs Q87-

I34.1 and Q87 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 I34.1
Marfan's syndrome (Q87.4-)
I34.1

Nonrheumatic mitral (valve) prolapse

Billable
Chapter 9
Diseases of the circulatory system
Section
I30-I5A
Use when the record says
  • Floppy nonrheumatic mitral valve syndrome
Indexed under
  • Floppy › nonrheumatic mitral valve syndrome
  • Prolapse, prolapsed › mitral (valve)
  • Syndrome › floppy › mitral valve
Q87

Other specified congenital malformation syndromes affecting multiple systems

Not billable
Chapter 17
Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders
Section
Q80-Q89

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