F84.2 — Rett's syndrome
Is F84.2 billable?
Yes — F84.2 is billable for FY2027. F84.2 is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. F84.2 may be submitted for encounters from October 1, 2026 through September 30, 2027.
F84.2 at a glance
| Code | F84.2 |
|---|---|
| Description | Rett's syndrome |
| Billable | Yes |
| Code set | ICD-10-CM FY2027 |
| Valid for encounters | October 1, 2026 – September 30, 2027 |
Which MS-DRGs does F84.2 group to?
F84.2 sits in MDC 01 and helps define the logic of 2 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.
- 056Degenerative Nervous System Disorders with MCCmedical
- 057Degenerative Nervous System Disorders without MCCmedical
As a secondary diagnosis, F84.2 is a complication or comorbidity (CC), which can move a stay into a higher-paying DRG.
How is F84.2 listed in the Alphabetic Index?
These are the routes through the Alphabetic Index that lead to F84.2. They show the wording a clinician may have documented, which often differs from the Tabular description.
- Rett's disease or syndrome
Excludes1 — never code together
The conditions below can never be reported together with F84.2 on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.
Excludes2 — not included here — inherited from Chapter 5
The conditions below are not part of F84.2, but a patient may have both at the same time. When documentation supports it, F84.2 and the excluded code may both be reported.
- symptoms, signs and abnormal clinical laboratory findings, not elsewhere classified (R00-R99)
Code also — inherited from F84
Two codes may be needed to describe the condition fully. Whether F84.2 is sequenced first depends on the reason for the encounter.
- any associated medical condition and intellectual disabilities
How long has F84.2 existed?
F84.2 has been in ICD-10-CM since at least FY2016, the earliest fiscal year on record here.
Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.
Which codes are confused with F84.2?
ICD-10-CM declares these codes mutually exclusive with F84.2 — exactly one of each pair can be correct for a given encounter.