Risk factors for acquired myasthenia gravis in dogs: 1,154 cases (1991–1995)

G. Diane Shelton From the Comparative Neuromuscular Laboratory, Department of Pathology, School of Medicine, University of California-San Diego, La Jolla, CA 92093-0612 (Shelton, Schule), and Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616-8734 (Kass).

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Alan Schule From the Comparative Neuromuscular Laboratory, Department of Pathology, School of Medicine, University of California-San Diego, La Jolla, CA 92093-0612 (Shelton, Schule), and Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616-8734 (Kass).

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Philip H. Kass From the Comparative Neuromuscular Laboratory, Department of Pathology, School of Medicine, University of California-San Diego, La Jolla, CA 92093-0612 (Shelton, Schule), and Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616-8734 (Kass).

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Objective

To determine frequency of initial clinical signs and risk factors for acquired myasthenia gravis (MG) in dogs.

Design

Retrospective study.

Sample Population

1,154 dogs residing within the United States from 1991 to 1995 with a confirmed diagnosis of acquired MG and 7,176 dogs with other neuromuscular disorders, including generalized weakness, megaesophagus, and dysphagia (control group).

Procedure

Records were retrieved from a database containing results of serum samples tested for acetylcholine receptor antibodies. Signalment, breed, age, state of origin, and month of onset of clinical signs were obtained. An antibody titer > 0.6 nmol/L was diagnostic for acquired MG. Unconditional logistic regression was used for statistical analysis.

Results

In comparison with mixed-breed dogs, dogs with the highest risk of acquired MG were Akitas, terrier group, Scottish Terriers, German Shorthaired Pointers, and Chihuahuas. Rottweilers, Doberman Pinschers, Dalmatians, and Jack Russell Terriers had low relative risks. Sexually intact males and dogs less than 1 year old had some protection from risk. Generalized weakness with megaesophagus and megaesophagus alone were the most common initial clinical signs.

Clinical Implications

Breed predispositions for acquired MG were demonstrated. Age and sex were contributing factors. Although most dogs had generalized clinical signs, a substantial proportion of dogs had focal signs. (J Am Vet Med Assoc 1997;211:1428–1431)

Objective

To determine frequency of initial clinical signs and risk factors for acquired myasthenia gravis (MG) in dogs.

Design

Retrospective study.

Sample Population

1,154 dogs residing within the United States from 1991 to 1995 with a confirmed diagnosis of acquired MG and 7,176 dogs with other neuromuscular disorders, including generalized weakness, megaesophagus, and dysphagia (control group).

Procedure

Records were retrieved from a database containing results of serum samples tested for acetylcholine receptor antibodies. Signalment, breed, age, state of origin, and month of onset of clinical signs were obtained. An antibody titer > 0.6 nmol/L was diagnostic for acquired MG. Unconditional logistic regression was used for statistical analysis.

Results

In comparison with mixed-breed dogs, dogs with the highest risk of acquired MG were Akitas, terrier group, Scottish Terriers, German Shorthaired Pointers, and Chihuahuas. Rottweilers, Doberman Pinschers, Dalmatians, and Jack Russell Terriers had low relative risks. Sexually intact males and dogs less than 1 year old had some protection from risk. Generalized weakness with megaesophagus and megaesophagus alone were the most common initial clinical signs.

Clinical Implications

Breed predispositions for acquired MG were demonstrated. Age and sex were contributing factors. Although most dogs had generalized clinical signs, a substantial proportion of dogs had focal signs. (J Am Vet Med Assoc 1997;211:1428–1431)

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