RISK-FACTORS FOR ACQUIRED MYASTHENIA-GRAVIS IN DOGS - 1,154 CASES (1991-1995)

Objective-To determine frequency of initial clinical signs and risk fa ctors for acquired myasthenia gravis (MG) in dogs. Design-Retrospectiv e study. Sample Population-1,154 dogs residing within the United State s from 1991 to 1995 with a confirmed diagnosis of acquired MG and 7,17 6 dogs with other neuromuscular disorders, including generalized weakn ess, megaesophagus, and dysphagia (control group). Procedure-Records w ere retrieved from a database containing results of serum samples test ed for acetylcholine receptor antibodies. Signalment, breed, age, stal e of origin, and month of onset of clinical signs were obtained. An an tibody titer > 0.6 nmol/L was diagnostic for acquired MG. Unconditiona l logistic regression was used for statistical analysis. Results-in co mparison 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 mal es and dogs less than 1 year old had some protection from risk. Genera lized weakness with megaesophagus and megaesophagus alone were the mos t common initial clinical signs. Clinical Implications-Breed predispos itions for acquired MG were demonstrated. Age and sex were contributin g factors. Although most dogs had generalized clinical signs, a substa ntial proportion of dogs had focal signs.