title: Myasthenia gravis in a polar bear (Ursus maritimus).
abstract: A 14.6-yr-old, female, multiparous polar bear (Ursus maritimus) acutely developed an apparent hind limb weakness. Physical examination and diagnostic tests including a hemogram, serum biochemistry, electrolytes, radiographs, and myelogram did not provide a definitive diagnosis. No improvement in condition was noted during 4 days of supportive care, and the bear was euthanized. An ovoid mass was present in the anterior mediastinum, and a thymoma was confirmed histologically. Compared with control polar bears, elevated serum acetylcholine receptor (AChR) antibodies (0.13 +/- 0.06 nmol/L vs. 0.86 nmol/L) were detected by immunoprecipitation radioimmunoassay, which is consistent with myasthenia gravis (MG) in other species. Although the AChR antibody test has not been validated in the polar bear, we are confident in the postmortem diagnosis of MG, which is commonly associated with thymoma in other species.
authors.affiliation: Denver Zoological Gardens, City Park, E. 2300 Steele Street, Denver, Colorado 80205-4899, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Kenny
authors.forename: Jeffery
authors.initials: J
authors.lastname: Baier
authors.forename: Felicia
authors.initials: F
authors.lastname: Knightly
authors.forename: Daniel
authors.initials: D
authors.lastname: Steinheimer
authors.forename: David M
authors.initials: DM
authors.lastname: Getzy
authors.forename: G Diane
authors.initials: GD
authors.lastname: Shelton
mesh_terms: D000818:Animals; D003937:Diagnosis, Differential; D017809:Fatal Outcome; D005260:Female; D009157:Myasthenia Gravis / Q000175:diagnosis / Q000209:etiology / Q000662:veterinary*; D013945:Thymoma / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D013953:Thymus Neoplasms / Q000150:complications / Q000175:diagnosis / Q000662:veterinary*; D001503:Ursidae