What Is It?
Familial dysautonomia (FD), also called Riley-Day syndrome, is an inherited disorder that affects the nervous system. The nerve fibers of people born with FD don't work properly. For this reason, they have trouble feeling pain, temperature, skin pressure and the position of their arms and legs. They can't fully experience taste.
In addition, people born with FD have a hard time regulating bodily functions, a condition called dysautonomia. These functions are managed by the autonomic nervous system — the network of nerves that controls such "automatic" functions as breathing and sweating.