Review articleMore research needed

Rett Syndrome: What's Happening Before the 'Regression' — and Why Early Signs Matter

A 2019 review study found that children with Rett syndrome may show subtle signs of the condition before the well-known regression at age 2, suggesting there may be an earlier window for diagnosis and support.

Educational summary - not medical advice. Always consult your child's care team.
Rett SyndromeDiagnosis·

Research Profile

Source:Neuroscience and Biobehavioral Reviews

Published: December 1, 2019

Added to SpecialCircle: July 25, 2026

Evidence Level

Review article

Research Status

More research needed

Key takeaways

  • •Rett syndrome is currently diagnosed based on a pattern where children seem to develop normally, then regress around age 2 — but this review challenges that idea.
  • •Researchers found evidence of subtle, early impairments in behavior, brain development, and physical health that appear before obvious symptoms.
  • •Some of these early changes may even begin during pregnancy (embryogenesis).
  • •Some early signs seem to fade on their own, which researchers think may be the body trying to compensate — but the underlying issues remain.
  • •The authors argue there is an urgent need for better tools to detect these early signs, so children can be identified and supported sooner.

Source

Neuroscience and Biobehavioral Reviews · Peer-reviewed study

Read the original source

Plain-language summary

For a long time, doctors believed that babies with Rett syndrome developed normally for the first year or two of life, and then suddenly got worse. This review of existing research — including studies on both children and animals — suggests that very subtle signs may actually be present much earlier than that.

Things like small differences in behavior, brain activity, and body function might be detectable before the obvious 'regression' begins. If researchers can find reliable early markers, it could open a window to diagnose children sooner and start supportive interventions at a younger age.

How it works

Science explained

Rett syndrome is caused by changes in brain development that researchers now believe may start as early as before birth, during a stage called embryogenesis. The brain and body show small, hard-to-spot differences early on — but some of these differences temporarily seem to disappear, possibly because the developing brain is trying to compensate or work around the problem. Over time, these compensatory mechanisms appear to break down, which may be what causes the more obvious regression seen around age 2.

Why parents may care

If you have a daughter with Rett syndrome — or are concerned about early development — this research suggests that the 'window of normal development' before regression may not be as clear-cut as once thought. Early, subtle signs may be present sooner, and researchers are working toward tools that could help catch them earlier so families can access support as soon as possible.

What this means for daily life

Right now, this research does not change day-to-day care or lead to new treatments. However, it encourages families and doctors to pay close attention to very early development in at-risk children, and it supports the push for earlier screening and intervention programs.

What is still unknown

Researchers do not yet have reliable, standardized tools to detect these early signs in everyday clinical practice. It is also unclear exactly which early markers are most meaningful, how consistently they appear across different children, and whether intervening during this early window actually improves long-term outcomes.

More systematic studies following children from birth are still needed.

Frequently asked questions about Rett Syndrome

Current diagnosis is based on the idea of normal early development followed by regression around age 2. However, this 2019 review found evidence of subtle early impairments in behavior, brain, and body that appear before obvious symptoms — suggesting the 'normal' period may not be entirely normal.

Terminology glossary

Regression
In Rett syndrome, regression refers to the period — usually around age 2 — when a child loses skills they had previously gained, such as hand use or speech.
Pre-symptomatic stage
The period before obvious symptoms appear; in Rett syndrome, this is the early window researchers are now studying for subtle, hidden signs of the condition.
Embryogenesis
The process of a baby developing in the womb; researchers suggest some of the biological roots of Rett syndrome may begin at this very early stage.
Compensatory mechanisms
Ways the brain or body tries to work around a problem; in Rett syndrome, some early signs may temporarily disappear because the developing brain is attempting to compensate.
Diagnostic markers
Measurable signs or features that doctors can use to identify a condition; researchers are looking for reliable early markers for Rett syndrome.
Animal models
Animals (often mice) that are used in research to study a disease; findings from animal models can suggest what might be happening in humans, though they don't always translate directly.

Questions to ask your doctor or therapist

  • ?Are there any early developmental signs in my daughter's history that could be connected to Rett syndrome?
  • ?Is there any early screening or monitoring I should know about for siblings or other at-risk children?
  • ?Could starting therapy or intervention earlier — before the regression — make a difference for my child?
  • ?Are there any research studies or registries we could participate in to help advance early detection?

⚕️ This research digest is for educational and community support purposes only. It is not medical advice, diagnosis, or treatment. Always speak with a qualified doctor, therapist, or medical professional before making decisions about care.

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