Rett Syndrome

A neurodevelopmental disorder that affects girls almost exclusively. It is typically seen in youngsters age six to 18 months and is characterized by normal early growth and development followed by a slowing of development, deceleration of head growth, deterioration of higher brain functions leading to profound intellectual disability or severe developmental delay and loss of purposeful use of the hands which is replaced by a constant hand washing movement in front of the face or chest. The inability to perform motor functions is perhaps the most severely disabling feature of Rett syndrome, interfering with every body movement, including eye gaze and speech. The course of Rett syndrome, including the age of onset and the severity of symptoms, varies from child to child. Nearly all cases are caused by a mutation in the MECP2 gene; and although Rett syndrome is a genetic disorder, most cases are spontaneous meaning that the mutation occurs randomly. Less than 1 percent of recorded cases are inherited or passed from one generation to the next. However, in some families of individuals affected by Rett syndrome, there are other female family members ("asymptomatic carriers") who have a mutation of their MECP2 gene but do not show clinical symptoms.