Rett syndromeRett syndrome is an inherited disorder that affects only females. The syndrome causes mental retardation and developmental degeneration. Rett Syndrome is a severe progressive neurological disorder that causes marked developmental regression, especially in the areas of expressive language and hand use. It occurs only in girls.
The gene associated with this disorder was recently identified on the X-chromosome. This gene encodes methl-CpG-binding protein 2 (MeCP2), which regulates synthesis (transcription) of various other proteins.
Synthesis of incorrect proteins, due to mutations in the gene, causes damage in the maturing brain. The severity of the disease is linked to specific types of mutation.
Rett Syndrome has an estimated prevalence of seven to ten cases per 100,000 females. Females have two X chromosomes, so even when one has this significant mutation, the other X chromosome provides enough normal protein for the child to survive.
Males conceived with this mutation are miscarried (spontaneously aborted) during pregnancy because they do not have a second X chromosome to compensate for the problem.
Most cases (99.5%) are due to spontaneous mutations, rather than inheritance. However, the incidence of familial cases is higher than would be expected by chance, so there may be an inherited factor involved.
Some of the most common symptoms are:
- Normal development during first months of infancy
- Hypotonia (floppy extremities) is frequently the first manifestation
- Head growth begins slowing (deceleration in head circumference) at approximately 5-6 months of age
- Developmental regression
- Language development, both expressed and understood, is severely impaired
- Loss of meaningful hand use, replaced by hand wringing or placement of hand in mouth
- Autistic-like behavior, loss of social engagement
- Seizures (1/3 of patients)
- Intermittent hyperventilation with a disorganized breathing pattern
The diagnosis of RS is based upon a thorough clinical evaluation including a complete physical and neurologic assessment; detection of characteristic symptoms and findings; and a careful patient and family history. Diagnostic studies may also be conducted to eliminate possible neurodegenerative, neurometabolic, mitochondrial, or other disorders that may have similar symptoms (e.g., Angelman syndrome, Batten disease, organic acidemias, lysosomal storage diseases, etc.). These studies may include certain blood and urine tests; analysis of cerebrospinal fluid (CSF); neurophysiologic tests, such as electromyography (EMG) and Nerve conduction velocity (NCV) studies; and neuroimaging techniques, including computerized tomography (CT) scanning or magnetic resonance imaging (MRI).
There is no cure for Rett syndrome; however, there are several treatments options. These include treatments for the orthopedic and learning disabilities and seizures that may occur in individuals with Rett syndrome. Some children may require special nutritional programs to maintain adequate weight.
In spite of the severe impairments that characterize this disorder, the majority of individuals with Rett can be expected to reach adulthood, surviving at least into their 40s. However, the risk of death is increased. Sudden, unexplained death -- possibly from brainstem dysfunction with respiratory arrest -- often occurs.