Can someone explain rett syndrome?

Disorder OF NERV SYS: Rett syndrome is a disorder of nervous system, it leads to developmental reversal, especially in areas of expression and hand use it happens mostly in girls and is often mis diagnosed as autism etc. There is normal development 6to18months symptoms vary mild and severe severe language/developmental problems, loss social intraction, loss of purposefull hand motions, ataxic gait, breathing problems, &more.