Rett syndrome is a rare genetic neurological disorder that primarily affects girls, causing a progressive loss of motor skills, speech, and purposeful hand use after a period of apparently normal early development. It occurs in roughly 1 in 10,000 to 15,000 female births, and while it was once considered a childhood condition with a shortened lifespan, current data shows that more than 70% of people with classic Rett syndrome survive past age 50.
What Causes Rett Syndrome
Nearly all cases of Rett syndrome are caused by a spontaneous mutation in a gene called MECP2, located on the X chromosome. This gene produces a protein that acts as a master regulator inside nerve cells, switching other genes on and off as the brain develops. It helps control how DNA is read and how brain cells communicate with each other. When the MECP2 protein doesn’t work properly, neurons can’t regulate themselves correctly, and this disrupts brain development and function on a broad scale.
The mutation is almost always random, not inherited from a parent. Because the gene sits on the X chromosome, girls (who have two X copies) are affected far more often than boys. Girls still have one working copy of the gene in some cells, which is partly why they survive. Boys with a fully nonfunctional MECP2 gene typically don’t survive infancy or present with severe brain damage. About 93% of diagnosed individuals are female.
How Symptoms Develop Over Time
Rett syndrome unfolds in a distinct pattern that can be broken into four phases, though the boundaries between them aren’t always sharp.
Early Onset Phase (Roughly 6 to 18 Months)
Babies with Rett syndrome were once thought to develop normally for their first six months, but video analysis of infants later diagnosed has revealed subtler problems from the start. In one study, all infants showed abnormal body movements from birth through six months, and 42% already displayed the repetitive hand movements that would become a hallmark later. During this phase, development stalls or stops. Slowing head growth is often one of the earliest visible signs.
Rapid Regression Phase (Roughly 1 to 4 Years)
This is the most alarming stage for families. Children lose skills they had previously gained, sometimes quickly. Purposeful hand movements and spoken language are typically the first to go. In their place, repetitive hand movements appear: wringing, squeezing, clapping, tapping, or a washing-like motion. Breathing irregularities often begin here as well, including episodes of hyperventilation and breath-holding during waking hours.
Plateau Phase (Preschool Through Much of Life)
The rapid loss of skills slows or stops, and some abilities may even improve slightly. Many people with Rett syndrome spend most of their lives in this phase. Seizures and movement difficulties are common during this stage, but some individuals develop stronger eye contact and non-verbal communication. Intense eye gaze, sometimes called “eye pointing,” often becomes a primary way of interacting with the world.
Late Motor Deterioration
In this phase, muscle tone changes significantly. Some individuals become increasingly stiff, while others lose muscle tone and become less mobile. Scoliosis can worsen to the point of requiring a brace or surgery. On the other hand, repetitive hand movements and breathing problems often become less frequent during this stage.
Breathing Problems in Rett Syndrome
Breathing disturbances are one of the more distinctive and distressing features. During the day, many individuals alternate between episodes of rapid, shallow breathing (hyperventilation) and prolonged breath-holds. These breath-holds resemble what happens during a Valsalva maneuver, where the body pushes air against a closed throat. Heart rate swings dramatically during these episodes, dropping during the pause and then surging when the breath-hold ends.
During sleep, the pattern shifts. Both central apneas (where the brain temporarily stops sending the signal to breathe) and obstructive apneas (where the airway physically closes) can occur, leading to brief dips in oxygen levels. These breathing irregularities are one reason close medical monitoring matters throughout life.
Common Health Complications
Beyond the core neurological symptoms, Rett syndrome brings a cluster of medical challenges that affect nearly every system in the body.
Epilepsy is one of the most common. About 72% to 84% of people with Rett syndrome develop seizures, with a typical onset around age 3. Seizure types and severity vary widely. Some respond well to medication, while others are more difficult to manage.
Scoliosis affects up to 94% of people with Rett syndrome, and the curvature can progress at a rate of 14 to 21 degrees per year. Severe cases lead to pain, loss of sitting balance, reduced lung capacity, and further loss of motor skills. Active postural programs and physical therapy can slow progression, but some individuals eventually need surgical correction.
Gastrointestinal problems are nearly universal. A large survey of nearly 1,000 families found that 92% of girls and women with Rett syndrome had symptoms related to slowed gut motility, including constipation and reflux. Chewing and swallowing difficulties affected 81%, weight problems affected 47%, and bone density issues or fractures affected 37%. These nutritional challenges persist throughout life and require ongoing attention.
How Rett Syndrome Is Diagnosed
Diagnosis rests on clinical observation, not a single test. The defining feature is a period of regression (loss of previously acquired skills) followed by stabilization or partial recovery. For a diagnosis of classic Rett syndrome, all four main criteria must be present: loss of purposeful hand skills, loss of spoken language, gait abnormalities or inability to walk, and stereotypic hand movements like wringing or clapping.
Doctors also apply exclusion criteria. If the developmental problems can be explained by brain injury from trauma, metabolic disease, or severe infection, Rett syndrome is ruled out. Severely abnormal development in the first six months also points away from a Rett diagnosis.
An atypical form of Rett syndrome can be diagnosed when a child shows the characteristic regression plus at least two of the four main criteria and five of eleven supportive signs. These supportive signs include breathing disturbances while awake, teeth grinding, disrupted sleep, abnormal muscle tone, cold hands and feet, scoliosis, growth problems, and episodes of inappropriate laughing or screaming. For children under 3 who carry an MECP2 mutation but haven’t yet shown clear regression, doctors may assign a “possible Rett syndrome” diagnosis and monitor closely.
Genetic testing for MECP2 mutations confirms the diagnosis in most cases, but the clinical picture is what drives the initial evaluation.
Treatment Options
In 2023, the FDA approved the first medication specifically for Rett syndrome: a twice-daily oral liquid for patients 2 years and older. It works by mimicking a naturally occurring growth factor in the brain that supports nerve cell health. The drug doesn’t cure the condition, but in clinical trials it improved symptoms related to daily functioning and behavior.
The most significant side effect is diarrhea, which occurred in 82% of patients in the pivotal trial compared to 20% on placebo. Vomiting affected 29%. These gastrointestinal side effects are considerable given that most people with Rett syndrome already have digestive challenges, so families and doctors weigh the benefits against this burden on a case-by-case basis.
Beyond medication, treatment is largely supportive and multidisciplinary. Physical therapy helps maintain mobility and slow scoliosis progression. Occupational therapy focuses on preserving whatever hand function remains and finding alternative ways to interact with the environment. Speech therapy, often centered on augmentative communication tools like eye-tracking devices, helps people with Rett syndrome express themselves despite the loss of spoken language. Seizure management with anti-epileptic medications is a major part of ongoing care for the majority of patients.
Life Expectancy and Long-Term Outlook
The outlook for Rett syndrome has improved substantially over the past few decades. At least 95% of people with classic Rett syndrome survive to age 20, about 80% reach age 35, and more than 70% live past 50. Death from extreme frailty has become rare. The most common causes of death are sudden unexplained events (possibly related to cardiac or breathing irregularities), pneumonia, and seizure complications.
Most individuals with Rett syndrome require lifelong, round-the-clock care. Many use wheelchairs by adulthood. But within those constraints, people with Rett syndrome remain emotionally engaged and responsive to the people around them. The intense eye communication that develops during the plateau phase is often described by families as deeply expressive, and many individuals show clear preferences, humor, and emotional connection throughout their lives.