Dysautonomia was diagnosed in 11 young (median age, 14-months), predom
inantly medium- to large-breed dogs from 1988 to 1995. Clinical signs
caused by autonomic dysfunction of the urinary, alimentary, and ocular
systems were most common. Dysuria, mydriasis, absence of pupillary li
ght reflexes, decreased tear production,dry mucous membranes, weight l
oss, and decreased anal tone were present in over 75% of affected dogs
. Ocular pharmacological testing with a dilute (0.1%) solution of pilo
carpine was used to demonstrate iris sphincter receptor function in al
l dogs. A low-dose (0.0375 mg/kg SC) bethanechol test and pharmacologi
cal testing with phenylephrine and epinephrine also demonstrated choli
nergic and adrenergic receptor function in 4 dogs. All dogs died or we
re euthanized as a result of autonomic dysfunction. Neuronal depletion
, with associated gliosis and minimal inflammation were noted histolog
ically in the autonomic ganglia of each dog. The pelvic, ciliary, celi
ac, cranial cervical, and cranial and caudal mesenteric ganglia were a
ffected in all dogs. The cause of autonomic failure in these dogs was
not determined. Copyright (C) 1996 by the American College of Veterina
ry Internal Medicine.