Any racial or ethnic group can experience Rett syndrome. Rett syndrome most commonly affects girls, although boys are also (rarely) affected. Boys are usually more severely affected than girls.
Nearly all cases of Rett syndrome are caused by a mutation in the methyl CpG binding protein 2, or MECP2 (pronounced meck-pea-two) gene. The MECP2 gene contains instructions for the synthesis of a protein called methyl cytosine binding protein 2 (MeCP2), which is needed for brain development and acts as one of the many biochemical switches that activate and deactivate gene functions. Because theMECP2 gene does not function properly in individuals with Rett syndrome, they may have too little MeCP2, or the MeCP2 they do have doesn’t work properly.
Not everyone who has an MECP2 mutation has Rett syndrome. Scientists believe some cases may be caused by partial gene deletions, mutations in other parts of the MECP2 gene, or additional genes that have not yet been identified. Genetic and environmental factors can contribute to differences in the severity and types of symptoms found in individuals with Rett syndrome. Those may include: where the MECP2 mutation is located in the gene, how the individuals’ sex chromosomes interact, and other genes can make the symptoms worse or protect from the effects of the mutation.
Although Rett syndrome is a genetic disorder, less than 1% of recorded cases are passed from one generation to the next. Most cases are spontaneous, which means the mutation occurs randomly. However, in some families of individuals affected by Rett syndrome, other family members have a mutation in the MECP2 gene. Families that already have an identified MECP2 mutation can get genetic testing to identify if they are carriers of the disorder.
NIH National Institute of Neurological Disorders and Stroke