Babies with Rett syndrome typically are born after a normal pregnancy and delivery. Most infants with Rett syndrome seem to grow and behave normally for the first six months. After that, signs and symptoms start to appear.

The most pronounced changes generally occur at 12 to 18 months of age, over a period of weeks or months. Symptoms and their severity can vary greatly from child to child.

Rett syndrome signs and symptoms include:

• Slowed growth. Brain growth slows after birth. Smaller than normal head size (microcephaly) is usually the first sign that a child has Rett syndrome. As children get older, delayed growth in other parts of the body becomes evident.
• Loss of normal movement and coordination. The first signs often include reduced hand control and a decreasing ability to crawl or walk normally. At first, this loss of abilities occurs rapidly and then it continues more gradually. Eventually muscles become weak or may become rigid or spastic with abnormal movement and positioning.
• Loss of communication abilities. Children with Rett syndrome typically begin to lose the ability to speak, to make eye contact and to communicate in other ways. They may become disinterested in other people, toys and their surroundings. Some children have rapid changes, such as a sudden loss of speech. Over time, children may gradually regain eye contact and develop nonverbal communication skills.
• Abnormal hand movements. Children with Rett syndrome typically develop repetitive, purposeless hand movements that may differ for each person. Hand movements may include hand-wringing, squeezing, clapping, tapping or rubbing.
• Unusual eye movements. Children with Rett syndrome tend to have unusual eye movements, such as intense staring, blinking, crossed eyes or closing one eye at a time.
• Breathing problems. These include breath-holding, abnormally rapid breathing (hyperventilation), forceful exhalation of air or saliva, and swallowing air. These problems tend to occur during waking hours, but breathing disturbances such as shallow breathing or periodic breathing can occur during sleep.
• Irritability and crying. Children with Rett syndrome may become increasingly agitated and irritable as they get older. Periods of crying or screaming may begin suddenly, for no apparent reason, and last for hours. Some children may experience fears and anxiety.
• Other abnormal behaviors. These may include, for example, sudden, odd facial expressions and long bouts of laughter, hand licking, and grasping of hair or clothing.
• Cognitive disabilities. Loss of skills can be accompanied by a loss of intellectual functioning.
• Seizures. Most people who have Rett syndrome experience seizures at some time during their lives. Multiple seizure types may occur and are accompanied by an abnormal electroencephalogram (EEG).
• Abnormal curvature of the spine (scoliosis). Scoliosis is common with Rett syndrome. It typically begins between 8 and 11 years of age and increases with age. Surgery may be required if the curvature is severe.
• Irregular heartbeat. This is a life-threatening problem for many children and adults with Rett syndrome and can result in sudden death.
• Sleep disturbances. Abnormal sleep patterns can include irregular sleep times, falling asleep during the day and being awake at night, or waking in the night with crying or screaming.
• Other symptoms. A variety of other symptoms can occur, such as thin, fragile bones prone to factures; small hands and feet that are usually cold; problems with chewing and swallowing; problems with bowel function; and teeth grinding.

Stages of Rett syndrome

Rett syndrome is commonly divided into four stages:

• Stage I: early onset. Signs and symptoms are subtle and easily overlooked during the first stage, which starts between 6 and 18 months of age and can last for a few months or a year. Babies in this stage may show less eye contact and start to lose interest in toys. They may also have delays in sitting or crawling.
• Stage II: rapid deterioration. Starting between 1 and 4 years of age, children lose the ability to perform skills they previously had. This loss can be rapid or more gradual, occurring over weeks or months. Symptoms of Rett syndrome occur, such as slowed head growth, abnormal hand movements, hyperventilating, screaming or crying for no apparent reason, problems with movement and coordination, and a loss of social interaction and communication.
• Stage III: plateau. The third stage usually begins between the ages of 2 and 10 years and can last for many years. Although problems with movement continue, behavior may have limited improvement, with less crying and irritability, and some improvement in hand use and communication. Seizures may begin in this stage and generally don't occur before the age of 2.
• Stage IV: late motor deterioration. This stage usually begins after the age of 10 and can last for years or decades. It's marked by reduced mobility, muscle weakness, joint contractures and scoliosis. Understanding, communication and hand skills generally remain stable or improve slightly, and seizures may occur less often.

Rett syndrome is a rare genetic disorder. Classic Rett syndrome, as well as several variants with milder or more-severe symptoms, can occur based on the specific genetic mutation.

The genetic mutation that causes the disease occurs randomly, usually in the MECP2 gene. Only in a few cases is this genetic disorder inherited. The mutation appears to result in problems with the protein production critical for brain development. However, the exact cause is not fully understood and is still being studied.

Rett syndrome in boys

Because males have a different chromosome combination from females, boys who have the genetic mutation that causes Rett syndrome are affected in devastating ways. Most of them die before birth or in early infancy.

A very small number of boys have a different mutation that results in a less destructive form of Rett syndrome. Similar to girls with Rett syndrome, these boys will likely live to adulthood, but they're still at risk of a number of intellectual and developmental problems.

Rett syndrome is rare. The genetic mutations known to cause the disease are random, and no risk factors have been identified. In a few cases, inherited factors — for instance, having close family members with Rett syndrome — may play a role.

Complications of Rett syndrome include:

• Sleep problems that cause significant sleep disruption to the person with Rett syndrome and family members
• Difficulty eating, leading to poor nutrition and delayed growth
• Bowel and bladder problems, such as constipation, gastroesophageal reflux disease (GERD), bowel or urinary incontinence, and gallbladder disease
• Pain that may accompany problems such as gastrointestinal issues or bone fractures
• Muscle, bone and joint problems
• Anxiety and problem behavior that may hinder social functioning
• Needing lifelong care and assistance with activities of daily living
• Shortened life span — although most people with Rett syndrome live into adulthood, they may not live as long as the average person because of heart problems and other health complications