Walsh & Hoyt: Familial Dysautonomia

Riley-Day syndrome, also called familial dysautonomia, is a rare disorder found almost exclusively in persons of Ashkenazi Jewish descent. The responsible gene maps to chromosome 9q3133 and is inherited in autosomal-recessive fashion. The diagnosis is suspected from clinical signs of generalized autonomic instability such as abnormal sweating, loss of vasomotor control, labile hypertension, episodic fever, and attacks of vomiting. Relative pain insensitivity and a peripheral sensory neuropathy are other features. Two ocular findings are present in all patients: absence or marked insufficiency of tears and corneal anesthesia. Diagnosis is based on five clinical signs: (a) lack of flare following intradermal histamine injection; (b) absence of fungiform papillae on the tongue; (c) pupillary miosis to dilute muscarinic agents such as pilocarpine (cholinergic denervation supersensitivity); (d) severe hypolacrimation; and (e) absent muscle-stretch reflexes.