Autosomal disorder of the peripheral and autonomic nervous systems limited to individuals of ashkenazic jewish descent; clinical manifestations are present at birth and include diminished lacrimation, defective thermoregulation, orthostatic hypotension, fixed pupils, excessive sweating, loss of pain and temperature sensation, and absent reflexes; pathologic features include reduced numbers of small diameter peripheral nerve fibers and autonomic ganglion neurons.

Familial dysautonomia (FD), also known as Riley–Day syndrome, is a rare, progressive, recessive genetic disorder of the autonomic nervous system that affects the development and survival of sensory, sympathetic, and some parasympathetic neurons in the autonomic and sensory nervous system. FD results in variable symptoms, including insensitivity to pain, inability to produce tears, poor growth, and labile blood pressure (episodic hypertension and postural hypotension). People with FD have frequent vomiting crises, pneumonia, problems with speech and movement, difficulty swallowing, and inappropriate perception of heat, pain, and taste, as well as unstable blood pressure and gastrointestinal dysmotility. Originally reported by Drs...