F84.2 vs F84.3
F84.2 and F84.3 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on F84.2
Other childhood disintegrative disorder (F84.3)
F84.2
Rett's syndrome
Billable
- Chapter 5
- Mental, Behavioral and Neurodevelopmental disorders
- Section
- F80-F89
Indexed under
- Rett's disease or syndrome
F84.3
Other childhood disintegrative disorder
Billable
- Chapter 5
- Mental, Behavioral and Neurodevelopmental disorders
- Section
- F80-F89
Use when the record says
- Dementia infantilis
- Disintegrative psychosis
- Heller's syndrome
- Symbiotic psychosis
Indexed under
- Heller's disease or syndrome
- Dementia › infantile, infantilis (degenerative (primary)) (persisting) (unspecified severity) (without behavioral disturbance, psychotic disturbance, mood disturbance, and anxiety)
- Disorder › childhood disintegrative NEC (of)
- Disorder › disintegrative, childhood NEC (of)
- Psychosis, psychotic › disintegrative
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