Definition

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

Causes

     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.

Signs and symptoms

     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.

Screening and diagnosis

     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

Complications

     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)

Treatment   

• Assistance with feeding, diapering, and treating symptoms like constipation and GERD).

• Supplemental feeding for those with slowed growth. Diets high in calories and fat, as well as nasogastric tube feeds, can help increase weight and height. Weight gain, in turn, may improve alertness and social interactions. If the person with Rett syndrome is prone to breathing in food, a feeding tube into the stomach may be recommended.

• Physical therapy for the hands to prevent them from contracting. Also, weight bearing exercises and frequent followup are recommended for those with scoliosis.

• Medication, like carbamazepine, to treat seizures.

     Other medications or supplements that have been used or studied include:

• L-dopa for motor rigidity in later stages of the disease

• L-carnitine -- some families report improvement in language skills, increased muscle mass, decreased constipation, increased alertness, less daytime sleeping, increased energy, and improved quality of life while their daughters took carnitine

• Folate and betaine

• Dextromethorphan

• Bromocriptine