Familial dysautonomia(FD,OMIM 223900;also known as HSAN Ⅲ or Riley-Day syndrome)is the most prevalent form of hereditary sensory and autonomic neuropathy(HSAN;Axelrod et al.,1974).Patients suffering from autonomic and sensory nervous system impairment have no available effective treatment and the average age of death is approximately 24 years.