F84.2 Rett's syndrome

The ICD-10-CM code for Rett's syndrome is F84.2 (FY2026). It is a billable, claim-ready diagnosis code.

Classification

Chapter

5: Mental, Behavioral and Neurodevelopmental disorders (F01-F99)

Section

F80-F89: Pervasive and specific developmental disorders (F80-F89)

Category F84

7 codes (6 billable)

FY2026 Status

Stable since FY2024

Also Known As

ICD-10-CM Alphabetic Index entries that lead to F84.2:

• Rett's disease or syndrome

U.S. Hospital Utilization

• An estimated 2,135 U.S. inpatient stays in 2023 included F84.2 among the documented diagnoses.
• 65 stays listed it as the principal diagnosis.

Source: National Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality, 2016–2023. National survey-weighted estimates.

Official Coding Guidelines

Pain disorders related to psychological factors (TOC entry)

a. Pain disorders related to psychological factors ..................................................................... 43

Psychoactive substance use disorders (TOC entry)

b. Mental and behavioral disorders due to psychoactive substance use ................................... 43

Source: CMS — ICD-10-CM Official Guidelines for Coding and Reporting, FY2026

References

• CMS — ICD-10-CM Official Code Set and Guidelines, FY2026
• CDC/NCHS — ICD-10-CM Files and Browser Tool
• AHRQ — HCUP National Inpatient Sample, Frequencies by Diagnosis Code (2016–2023)