Downs syndrome - possible fix.

The BBC reports there may be a way to turn off the third copy of human chromosome 21 which produces Downs Syndrome.  In a lab setting, Dr. Jeanne Lawrence's team at the University of Massachusetts Medical School inserted the XIST gene into stem cells grown from a Downs Syndrome person and were successful in shutting down the entire effects of the third copy of chromosome 21.

Picture from BBC story

The write up leans to "more research required" rather than "exciting breakthrough" but the proof of concept is there.