Rett syndrome
Overview
Rett syndrome is a rare genetic disorder that affects brain development, resulting in severe mental and physical disability.
Symptoms
Some children with Rett syndrome are affected more severely than others. Also, the age at which symptoms first appear varies from child to child. A child may not have all the symptoms of Rett syndrome, and their symptoms might change as they get older. Rett syndrome is described in 4 stages, although symptoms will often overlap between each stage. These are the main features of each stage: At first, the child will appear to develop and grow normally for at least 6 months. There may be subtle signs of Rett syndrome before the child is recognised as having a problem (especially with hindsight). Stage 1 is sometimes described as "stagnation". Symptoms include: low muscle tone (hypotonia)difficulty feedingunusual, repetitive hand movements or jerky limb movementsdelay with development of speechmobility problems, such as problems sitting, crawling and walkinglack of interest in toys These symptoms typically begin from 6 to 18 months and often last for several months, although they can persist for a year or more. Stage 1 can often go unnoticed because the changes occur gradually and may be subtle.
Causes
Almost all cases of Rett syndrome are caused by a mutation (a change in the DNA) in the MECP2 gene, which is found on the X chromosome (one of the sex chromosomes). The MECP2 gene contains instructions for producing a particular protein (MeCP2), which is needed for brain development. The gene abnormality prevents nerve cells in the brain from working properly. There's usually no family history of Rett syndrome, which means it's not passed on from one generation to the next. Almost all cases (over 99%) are spontaneous, with the mutation occurring randomly.