Rett Syndrome

http://www.news.com.au/heraldsun/story/0,21985,21215636-662,00.html

Children suffering from Rett syndrome, the most physically debilitating of
all the Autism disorders, usually die in their early teens. Researchers
at Edinburgh Univerisity have located the gene responsible for this
disorder. After replacing the gene MECP2 in mice, the symptoms
disappeared. There is a long way to go before knowing if this is a
potential treatment of cure, but the research definately shows promise. Ms
Morriss, whos daughter was diagnosed with Rett's said "I think it is a
huge development, the biggest since they discovered the disease and gave
it a name in 1983."