Rett Syndrome: Causes, Signs, Stages, and Treatment
Rett syndrome is a rare genetic neurodevelopmental disorder, typically caused by a mutation in the MECP2 gene on the X chromosome. It affects girls almost exclusively. Development usually appears typical until somewhere between six and 18 months, followed by a period of regression involving loss of purposeful hand use and spoken language, the emergence of repetitive hand movements such as wringing or clapping, and difficulties with walking and coordination. Rett syndrome was listed among the pervasive developmental disorders in the DSM-IV but was removed from the autism category entirely in the DSM-5 in 2013. It is a genetic condition with its own diagnostic pathway and its own treatment, not a type of autism.
What causes Rett syndrome
Rett syndrome is typically caused by a mutation in MECP2, a gene on the X chromosome that produces a protein needed for normal brain development. When MeCP2 protein function is deficient, communication between brain cells is impaired, and that impairment appears to underlie the features of the condition.
Why it affects girls almost exclusively. MECP2 sits on the X chromosome. Girls have two X chromosomes, so a mutation on one is partially offset by the other. Boys have only one, and the effect is usually far more severe; most do not survive infancy. A small number of males are affected, generally through different genetic mechanisms.
It is not usually inherited. The great majority of MECP2 mutations arise spontaneously rather than being passed down, and parents very rarely carry the mutation. This is one of the first questions most families ask, and the answer is usually reassuring.
Diagnosis is genetic. Clinical criteria guide suspicion, but genetic testing for MECP2 confirms the diagnosis. If your child has been given a clinical diagnosis without genetic testing, it's worth asking about — the result affects access to treatment and to research studies. Rett syndrome is estimated to affect roughly 6,000 to 9,000 people in the United States.
Why Rett syndrome is not a type of autism
The DSM-IV listed five conditions under pervasive developmental disorders: autistic disorder, Asperger's disorder, PDD-NOS, childhood disintegrative disorder, and Rett syndrome. When the DSM-5 was published in May 2013, four of those were merged into a single autism spectrum disorder diagnosis. Rett syndrome was not. It was removed from the autism category altogether.
The reasoning is straightforward: Rett has a known single-gene cause, a distinctive and predictable clinical course, and diagnostic and treatment pathways that don't resemble autism's. Grouping it with autism obscured all of that.
Some overlap in presentation is real. During the regression stage in particular, features can resemble autism — loss of social engagement, loss of language, repetitive movements. That's part of why the conditions were grouped historically, and why some girls with Rett received an autism diagnosis first. The DSM-5 does allow a person to be diagnosed with autism spectrum disorder "associated with a known genetic condition" where they meet autism criteria as well. But Rett is not a subtype of autism, and treating it as one delays the genetic testing that actually determines care.
The four stages
Rett syndrome typically progresses through four stages. Individual experience varies considerably, and these describe a general pattern rather than a schedule.
Stage 1 — Early onset (roughly 6 to 18 months)
Development slows. Changes can be subtle: less eye contact, reduced interest in toys, delays in sitting or crawling, some loss of muscle tone. This stage is often recognized only in retrospect.
Stage 2 — Regression (roughly 1 to 4 years)
The most noticeable period. Loss of purposeful hand use and of spoken language, often over weeks to months. Characteristic repetitive hand movements emerge — wringing, washing, clapping, mouthing. Breathing irregularities, difficulty with social interaction, and slowed head growth are common.
Stage 3 — Plateau (often lasting years)
Regression stops. Many girls show improvement in alertness, communication, and social engagement, even as motor difficulties and hand stereotypies persist. Seizures and breathing irregularities are common in this stage. Many families describe this period as considerably better than they had been prepared for.
Stage 4 — Late motor deterioration
Reduced mobility, muscle weakness, spasticity, and scoliosis. Hand stereotypies may decrease. Cognitive ability and communication generally do not decline further in this stage, and most people with Rett syndrome live into adulthood.
Treatment and management
Trofinetide (Daybue) was approved by the FDA in March 2023 — the first medication approved specifically for Rett syndrome, for adults and children aged two and over. It is a synthetic analogue of a peptide derived from IGF-1. The approval was supported by the Phase 3 LAVENDER study, which evaluated trofinetide against placebo in 187 female patients aged five to 20 and met both of its co-primary efficacy endpoints. Diarrhea and vomiting are the most commonly reported side effects. A powder formulation, Daybue STIX, was subsequently approved, offering an alternative to the oral solution.
Trofinetide is not a cure. It targets underlying biology rather than only symptoms, and reported benefits center on communication, motor function, and social engagement. Suitability is a conversation for your child's specialist.
Therapy is central and multidisciplinary:
- Physical therapy — mobility, positioning, scoliosis management, maintaining range of movement.
- Occupational therapy — hand use, daily activities, seating, sensory needs.
- Speech and language therapy — communication systems including eye-gaze technology and AAC. Many girls with Rett communicate effectively with the right tools; loss of speech is not loss of communication.
- Medical management — seizures, breathing irregularities, scoliosis, gastrointestinal issues, bone health, and sleep.
Research is active. Gene therapy and other disease-modifying approaches are in development, and the International Rett Syndrome Foundation maintains current information on trials.
Find providers: physical therapy · occupational therapy · speech therapy
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Browse the DrSensory Therapy Directory →Where sensory processing fits
Sensory processing differences are commonly reported in Rett syndrome, and they interact with almost everything else — tolerance for positioning and handling, response to noise and touch during therapy, and communication in busy environments. ICD-11, effective 2022, formally added sensory processing differences to the diagnostic criteria for autism, which has raised clinical attention to sensory features across neurodevelopmental conditions generally. For Rett specifically, an occupational therapist can assess sensory processing as part of the wider picture, and small environmental adjustments frequently make therapy sessions substantially more productive.
Sensory processing differences · vestibular and proprioceptive processing
Support for families
- International Rett Syndrome Foundation — research funding, family support, and current trial information.
- Specialist Rett clinics exist in many regions and are worth seeking out; multidisciplinary care makes a substantial practical difference.
- Genetic counseling — even though most cases arise spontaneously, counseling is worth having for family-planning questions.
Frequently asked questions
Is Rett syndrome a type of autism?
No. Rett syndrome was listed among the pervasive developmental disorders in the DSM-IV but was removed from the autism category entirely in the DSM-5 in 2013. It is a genetic condition with its own diagnostic pathway. A person with Rett syndrome can also receive an autism diagnosis if they meet autism criteria, but Rett is not an autism subtype.
What causes Rett syndrome?
It is typically caused by a mutation in the MECP2 gene on the X chromosome. The great majority of these mutations arise spontaneously rather than being inherited.
Is Rett syndrome inherited?
Usually not. Most MECP2 mutations occur spontaneously and parents very rarely carry the mutation. Genetic counseling can address family-planning questions.
Can boys have Rett syndrome?
Rarely. MECP2 is on the X chromosome, and boys have only one X, so the effect is usually far more severe; most do not survive infancy. A small number of affected males exist, generally through different genetic mechanisms.
Is there a treatment for Rett syndrome?
Trofinetide (Daybue) was approved by the FDA in March 2023 for adults and children aged two and over — the first medication approved specifically for Rett syndrome. It is not a cure. Physical, occupational, and speech therapy remain central, alongside medical management of seizures, breathing, and scoliosis.
Do girls with Rett syndrome understand what's happening around them?
Loss of speech is not loss of comprehension or communication. Many girls with Rett communicate effectively using eye-gaze technology and other AAC systems. Assume understanding and provide access to communication tools.
How is Rett syndrome diagnosed?
Clinical features guide suspicion, and genetic testing for MECP2 mutations confirms the diagnosis. If a clinical diagnosis was made without genetic testing, ask about it — the result affects treatment access and research eligibility.
References
- Neul, J. L., et al. (2023). Trofinetide for the treatment of Rett syndrome: a randomized phase 3 study (LAVENDER). Nature Medicine.
- Keam, S. J. (2023). Trofinetide: First Approval. Drugs. PMID 37191913.
- Acadia Pharmaceuticals (March 10, 2023). FDA approval of DAYBUE (trofinetide) for Rett syndrome, ages two and older.
- U.S. National Library of Medicine, MedlinePlus Genetics — Rett syndrome. medlineplus.gov
- International Rett Syndrome Foundation. rettsyndrome.org
Medical disclaimer. This page is for general educational purposes and does not constitute medical advice, diagnosis, or treatment. Genetic conditions require individualized specialist care. Always consult a qualified healthcare provider about your individual situation.
