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Rett Syndrome
Printer-friendly versionRett Syndrome (RS) is a unique developmental disorder, which begins to show its affects in infancy or early childhood. It is seen almost exclusively in girls, although it can occur rarely in boys. It is found in a variety of racial and ethnic groups throughout the world.
Rett syndrome is caused by a mutation (change) on the MECP2 gene of the X chromosome. The MECP2 gene is responsible for turning off other genes when they are no longer needed in development (most genes are active for only a specific period in development and then shut off forever.) The MECP2 mutation causes the turn-off mechanism to fail, allowing other genes to stay active when they are no longer needed, and allowing proteins and enzymes to build up and become toxic to the central nervous system. So, RS is a genetic disorder of developmental arrest or failure of brain maturation. This is thought to occur when subsets of neurons and their connections (synapses) are disrupted during a very dynamic phase of brain development. This deviation occurs in the first few months of life, when synapses are normally being overproduced, only to be pruned later on to the normal adult number. In RS, these synapses appear to be under produced, or possibly over pruned.
RS results from a chain of events beginning with the MECP2 genetic mutation. Mutations occur naturally in everyone all the time and most do not cause problems. The MECP2 mutation results in a shortage or absence of MeCP2 protein needed to direct other genes. These downstream genes produce proteins or factors, which control the normal development of selected regions of the brain responsible for sensory, emotional, motor and autonomic function. Development appears to be normal in early infancy until the factors are needed to be active or inactive, for further brain development. Without these factors, selected regions of the brain remain developmentally immature. This explains why the child appears to be developing normally in the first months of life.
The chance of having more than one child with RS is very small, less than one percent. This means that more than 99% of the time, the mutation is sporadic, just occurs on its own and is not repeated in a family.
The age when RS begins and the severity of different symptoms may vary. The child with RS is usually born healthy and shows an early period of apparently normal or near normal development until 6-18 months of life, when there is a slowing down or stagnation of skills. A period of regression then follows when she loses communication skills and purposeful use of her hands. Soon, stereotyped hand movements, gait disturbances, and slowing of the normal rate of head growth become apparent. Other problems may include seizures and disorganized breathing patterns, which occur when she is awake. There may be a period of isolation or withdrawal when she is irritable and cries inconsolably. Over time, motor problems may increase, while other symptoms may decrease or improve.
Rett syndrome is not a degenerative disorder, but it is a developmental disorder. Barring illness or complications, survival into adulthood is expected.