RETT SYNDROME

OVERVIEWRett syndrome is a neurodevelopmental disorder occurring almost exclusively in females that affects development after an initial 6-mo period of normal development. Diagnosis is based on clinical observation of signs and symptoms during the child's early growth and development, regular ongoing evaluations of the child's physical and neurologic status and genetic testing to search for the MECP2 gene mutation on the child's X chromosome (Xq28). Treatment involves a multidisciplinary approach that focuses on the management of symptoms.

INTRODUCTION• Rett Syndrome is estimated to affect 1 in every

10,000 to 15,000 live female births in all racial and ethnic groups worldwide.

• Most cases are random, spontaneous mutations; < 1% of recorded cases are inherited or passed from one generation to the next.

• Girls with the typical clinical picture of Rett syndrome are usually born at term after an uneventful pregnancy and delivery.

• Boys are rarely affected.

ETIOLOGY• Usually Rett syndrome is caused by a mutation in the

methyl CpG binding protein 2 ( MECP2 ) gene. The MECP2 gene is involved in the production of a protein called methyl-cystine binding protein 2 ( MeCP2) which is needed for brain development and acts as a biochemical switch that can either increase gene expression or tell other genes when to turn off and stop producing their own unique proteins. The MECP2 gene does not function normally in Rett syndrome so that structural abnormal forms or inadequate amounts of the protein are produced and can cause other genes to have abnormal gene expression.

RESEARCH• Rett syndrome is not always caused by a MECP2

mutation but may be caused by partial gene deletions, mutations in other genes (eg, CDKL5 and FOXG1 genes) that affect brain development in atypical Rett syndrome, mutations in other parts of the MECP2 gene, and possibly other genes that have not yet been identified.

• FOXG1: specific function has not yet been determined; however, it may help in brain and telencephalon (cerebrum) development

• CDKL5: essential in normal brain development; acts as a kinase

CLINICAL FEATURES• The course, age of onset, and severity of

symptoms of Rett syndrome vary from child to child.

• Rett syndrome is characterized by normal early growth and development followed by slowing of developmental milestones, and then regression of skills with loss of purposeful hand use with compulsive hand wringing and washing behavior, slowed head and brain growth, seizures, walking difficulty, and intellectual disability.

• There are 4 stages used to describe the symptoms of Rett syndrome:

CLINICAL FEATURES• Stage 1 ( early onset) usually begins when the child is between 6

and 18 mo old with subtle slowing of development. Symptoms may include less eye contact, decreased interest in toys, delays in sitting or crawling, decreased head growth, and hand-wringing.

• Stage 2 (developmental regression or rapid destructive stage) usually begins between ages 1 and 4 yr. The onset may be rapid or gradual with loss of purposeful hand skills and spoken language. During this stage, characteristic hand movements begin such as wringing, clapping, washing, tapping and repeatedly bringing the hands to the mouth. The movements disappear during sleep. Breathing irregularities may occur, such as episodes of apnea and hyperventilation. Walking may be unsteady, and initiating motor movements may be difficult. Some girls may also have symptoms similar to those of autism spectrum disorders, such as impaired social interaction and impaired communication

CLINICAL FEATURES• Stage 3 (pseudostationary stage) usually begins between

ages 2 and 10 yr and can last for years. Seizures, motor deficits, and apraxia are common during this stage. Sometimes, symptoms such as crying, irritability, and autism-like symptoms decline during this stage. Alertness, communication skills, attention span, and interest in the surroundings may increase during this stage.

• Stage 4 (late motor deterioration stage) can last for years or decades. Common characteristics include scoliosis, decreased mobility, muscle weakness, spasticity, or rigidity. Sometimes walking may stop. Eye gaze for communication purposes becomes prominent as spoken language is absent, and repetitive hand movements may decrease.

• Children may develop scoliosis. Cardiac abnormalities (such as prolonged QT interval) are often present. Affected children may have slowed growth and tend to have difficulty maintaining weight.

DIAGNOSISClinical & Genetic testingDiagnosis is made clinically by observing signs and symptoms during the child’s early growth and development. Ongoing evaluation of the child’s physical and neurologic status is needed.

Genetic testing for the MECP2 mutation on the X chromosome (Xq28) is used to complement the clinical diagnosis.

DIAGNOSIS• The National Institute of Neurological Disorders and Stroke (NINDS)

provides guidelines used to confirm the clinical diagnosis of Rett syndrome. These guidelines divide the clinical diagnostic criteria into main, supportive and exclusion.

• The main diagnostic criteria include loss of all or part of purposeful hand skills, repetitive hand movements ( such as wringing or squeezing, clapping or rubbing), loss of all or part of spoken language, and gait abnormalities including toe-walking, unsteady, wide-based or stiff-legged walk.

• The supportive criteria are not required for a diagnosis of Rett syndrome but may occur in some children. A child with supportive criteria but none of the main criteria does not have Rett syndrome. Supportive criteria include scoliosis, teeth-grinding, abnormal sleep patterns, small hands and feet in relation to height, cold hands and feet, abnormal muscle tone, intense eye communication, inappropriate laughing or screaming, and decreased response to pain.

DIAGNOSIS• The exclusion criteria include the presence of

other disorders that cause similar symptoms, including traumatic brain injury, grossly abnormal psychomotor development during the first 6 mo, and severe infection causing neurologic problems.

TREATMENTManagement of symptomsMultidisciplinary team support• There is no cure for Rett syndrome. Treatment is optimal with a

multidisciplinary approach to address symptoms and signs.

• A program of occupational therapy, physical therapy, and communication therapy (with a speech and language therapist) should be provided to address self-help skills such as feeding and dressing, limited mobility, walking difficulty, and communication deficits.

• Drugs may be needed to control seizures, for breathing dysfunction or motor difficulties

• Regular re-evaluation is needed for scoliosis progression and to follow cardiac abnormalities.

• Nutrition support may be needed to help affected children maintain weight. Special education programs and social and support services are needed.

TREATMENT• Medications

o Medications can be taken to help with the symptoms like seizures and muscle stiffness, but can't be taken to cure the disease• Bromocriptine: test trials with Rett syndrome patients have been

used to improve relaxation and communication skills• Dextromethorphan: being used to determine if DM will prevent

the harmful over-stimulation of the neurons thereby reducing EEG spike activity and aims to find out which dose if any will help improve EEG abnormalities, behavior, cognition, and reduce seizures, as well as improve breathing abnormalities, motor capabilities, bone density, and GI dysfunction.

• Folate and betaine• L- carnitine: which may help improve language skills, muscle

mass, alertness, energy and quality of life while decreasing constipation and daytime sleepiness

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

PROGNOSIS• Rett syndrome is rare, so there is little

information about long-term prognosis and life expectancy beyond about age 40. Sometimes cardiac abnormalities may predispose children with Rett syndrome to sudden death but usually children survive well into adulthood with comprehensive, multidisciplinary team support.