2026 ICD-10-CM Diagnosis Code F84.2Rett's syndrome
ICD-10-CM Codes›F01–F99›F80-F89›F84
- Billable — Valid for Submission
- Chronic Condition
F84.2 is a billable ICD-10-CM diagnosis code for Rett's syndrome. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026). Coders also document this condition as atypical Rett syndrome. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Neurodevelopmental disorders.
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Atypical Rett syndrome
- Dementia due to genetic disease
- Dementia due to Rett syndrome
- Dystonia due to Rett syndrome
- MECP2 related disorder
- Rett syndrome
Tabular List NotesGuidance
Coding notes and annotation back-references applicable to this code.
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
- Rett's disease or syndrome - F84.2
External Cause of Injuries IndexGuidance
References for this code in the External Cause of Injuries Index.
- Rett's disease or syndrome
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Rett Syndrome
an inherited neurological developmental disorder that is associated with x-linked inheritance and may be lethal in utero to hemizygous males. the affected female is normal until the age of 6-25 months when progressive loss of voluntary control of hand movements and communication skills; ataxia; seizures; autistic behavior; intermittent hyperventilation; and hyperammonemia appear. (from menkes, textbook of child neurology, 5th ed, p199)
Patient EducationClinical
Rett Syndrome
Rett syndrome is a rare genetic disease that causes developmental and nervous system problems, mostly in girls. It's related to autism spectrum disorder. Babies with Rett syndrome seem to grow and develop normally at first. Between 3 months and 3 years of age, though, they stop developing and even lose some skills. Symptoms include:
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert F84.2 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About F84.2Overview
Is F84.2 (Pervasive developmental disorders) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report Rett's syndrome on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What is the ICD-9 equivalent of F84.2?
Under the General Equivalence Mappings, Rett's syndrome converts to ICD-9-CM 330.8 (cereb degen in child NEC). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:
- The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
- The condition places limitations on self-care, independent living, and social interactions.
