Risk factors for acquired myasthenia gravis in cats: 105 cases (1986-1998).
OBJECTIVE
To determine prevalence of initial clinical signs and risk factors for acquired myasthenia gravis (MG) in cats.


METHODS
Retrospective case-control study.


METHODS
105 cats from the United States, Canada; and the United Kingdom with a confirmed diagnosis of acquired MG and 510 cats with other neuromuscular disorders, including generalized weakness, megaesophagus, and dysphagia (control group).


METHODS
Records were retrieved from a data-base containing results of serum samples tested for acetylcholine receptor antibodies. Signalment, including breed, age, and state or country of origin, month of onset, and initial clinical signs were obtained. An acetylcholine receptor antibody titer > 0.3 nmol/L was diagnostic for acquired MG. Unconditional logistic regression was used for statistical analysis.


RESULTS
Compared with mixed-breed cats, the breed with the highest relative risk of acquired MG was the Abyssinian (including Somali). Significant differences between sexes were not detected. There was no compelling evidence for a difference in risk of developing MG between states or countries. Relative risk increased after 3 years of age. The most common clinical signs were generalized weakness without megaesophagus and weakness associated with a cranial mediastinal mass. Focal signs, including megaesophagus and dysphagia without signs of generalized weakness, were also evident.


CONCLUSIONS
A breed predisposition for acquired MG in Abyssinians (and related Somalis) was observed. Clinical signs were variable and included generalized weakness, megaesophagus, and dysphagia. A cranial mediastinal mass was commonly associated with MG in cats.
Shelton
G D
GD
Department of Pathology, School of Medicine, University of California-San Diego, La Jolla 92093-0612, USA.
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M
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Kass
P H
PH
D000367:Age Factors; D000818:Animals; D001323:Autoantibodies / Q000097:blood; D001947:Breeding; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D002371:Cat Diseases / Q000453:epidemiology*; D002415:Cats; D005260:Female; D016015:Logistic Models; D008297:Male; D009157:Myasthenia Gravis / Q000175:diagnosis / Q000453:epidemiology / Q000662:veterinary*; D015995:Prevalence; D011863:Radioimmunoassay / Q000662:veterinary; D011950:Receptors, Cholinergic / Q000276:immunology*; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology
D001323:Autoantibodies; D011950:Receptors, Cholinergic