CHILDREN'S HEALTH Birth Defects • Down syndrome • Fetal alcohol syndrome • Phenylketonuria • Ambiguous genitalia • Rett syndrome • Cleft lip and cleft palate • Familial Mediterranean fever • Clubfoot

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Rett syndrome is a developmental disorder that affects brain growth. Occurring almost exclusively in girls, this disorder produces severe autism-like symptoms.

Babies with Rett syndrome typically have no signs or symptoms during the first six months of life. Between the ages of 6 months and 18 months, however, they stop improving their speech and hand skills and begin to lose ground generally.

Caused by a mutated gene, Rett syndrome occurs in about one in 23,000 births. Boys who inherit this mutated gene usually don't survive infancy.

There is no cure for Rett syndrome, but therapy helps some affected children improve their functional motor and communication skills.

Rett syndrome's signs and symptoms vary, depending on the stage and severity of the disease. The disorder is commonly divided into four stages:

• Stage I. Signs and symptoms are subtle and easily overlooked during the first stage of Rett syndrome, which starts between 6 months and 18 months of age. Babies in this stage of Rett syndrome may show less eye contact and start to lose interest in toys. There also may be delays in sitting or crawling.
• Stage II. Starting between ages 1 and 4 years, children with Rett syndrome gradually lose the ability to speak and to use their hands purposefully. Repetitive, purposeless hand movements — wringing, washing, clapping or tapping — begin during this stage. Some girls with Rett syndrome have irregular breathing, either holding their breath or hyperventilating. They may scream or cry without provocation. It's often difficult for them to initiate movement. Slowing of head growth usually is noted during this stage.
• Stage III. The third stage is a plateau that usually begins between the ages of 2 and 10 years and can last for years. While problems with mobility continue, behavior may improve. Girls in this stage often have less crying and irritability, and can show an improvement in alertness, attention span and nonverbal communication skills. Many girls with Rett syndrome remain in stage III for the remainder of their lives.
• Stage IV. The last stage is marked by reduced mobility, muscle weakness and scoliosis — an abnormal curvature of the spine. Understanding, communication and hand skills, however, typically don't decline further during this stage. In fact, repetitive hand movements may decrease. While sudden death in sleep can occur, most women with Rett syndrome live into their 40s or 50s.

Rett syndrome is caused by a mutated gene on the X chromosome. Girls have two X chromosomes in each cell of their bodies. Since each cell needs only one working copy of the gene, each cell automatically inactivates one of its two X chromosomes. The severity of Rett Syndrome varies by individual, and it is thought to be linked to the percentage of cells that inactivate the X chromosome with the mutated gene — the more cells that have the mutated gene inactivated, the less severe the symptoms of Rett syndrome will be.

Boys have only one X chromosome, so if boys have the gene mutation that causes Rett syndrome, all of their cells have the mutated gene, and they usually die in infancy. The gene mutation that causes Rett syndrome occurs randomly and spontaneously, so Rett syndrome doesn't run in families. Less than 1 percent of recorded cases are passed from one generation to the next.

Genetic testing of a blood sample can detect the gene defect that causes Rett syndrome. Before ordering this expensive blood test, doctors usually try to establish the diagnosis based on signs and symptoms.

A diagnosis of Rett syndrome requires the following criteria:

• Apparently normal development until at least the age of 6 months
• Normal head circumference at birth, followed by slowing of head growth
• Severely impaired language skills
• Repetitive hand movements
• Shaking of the torso
• Toe walking or an unsteady, wide-based gait

Most girls with Rett syndrome have trouble with the physical mechanics of eating, so they often are shorter and weigh less than other children their age. To maintain proper nutrition, some girls need to be fed through tubes into their stomachs. Constipation can be a severe and chronic problem.

Other common problems include:

• Epilepsy
• Cardiac arrhythmias
• Bone fractures
• Scoliosis (abnormal curvature of the spine)

No medicine can cure Rett syndrome. However, drugs may help control some of the symptoms associated with the disorder — such as epileptic seizures. Orthopedic surgery may be needed for severe cases of scoliosis.

In some cases, physical therapy can help maintain walking skills, and occupational therapy may improve purposeful use of the hands. If repetitive arm and hand movement is a problem, splints that restrict elbow or wrist motion may be helpful. Children with Rett syndrome may show improvements in their overall functioning when their habitual movement is disrupted.

Children with Rett syndrome need help with most daily tasks, such as eating, walking and toileting. This constant care can be exhausting and stressful for families. It is natural to feel overwhelmed at times. Talking about your problems can help relieve your feelings of stress. Arrange for outside help to ease your load.

Many families affected by Rett syndrome care for their children at home, often with the help of outside caregivers who can give parents a break. Other families choose residential care, especially when their children become adults.

Each family and each child with Rett syndrome is different. But connecting with other families facing the same problems can help you feel less alone. Online support and information are available from the International Rett Syndrome Association.