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  • Author or Editor: G. Diane Shelton x
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Abstract

Objective—To determine prevalence of initial clinical signs and risk factors for acquired myasthenia gravis (MG) in cats.

Design—Retrospective case-control study.

Animals—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).

Procedures—Records were retrieved from a database 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 and Clinical Relevance—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. ( J Am Vet Med Assoc 2000;216:55–57)

Full access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

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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in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

CASE DESCRIPTION

A 4.5-year-old neutered male domestic ferret (Mustela putorius furo) was examined because of clinical signs compatible with neuromuscular disease.

CLINICAL FINDINGS

Results of electrophysiologic assessment, including measurement of compound muscle action potentials following repetitive nerve stimulation, and measurement of the anti–acetylcholine receptor antibody titer were consistent with a diagnosis of acquired myasthenia gravis.

TREATMENT AND OUTCOME

Medical treatment with pyridostigmine and prednisolone was instituted. The first signs of clinical improvement were observed 2 months later, followed by a slow but steady improvement over the next months. Anti–acetylcholine receptor antibody titer was measured 10 months after initiation of treatment and was markedly decreased, compared with the initial titer. Pyridostigmine and prednisolone dosages were tapered over the following 4 months without any evidence of recurrence of clinical signs. Thirty months after initial examination, the ferret was clinically normal and not receiving any treatment. A follow-up anti–acetylcholine receptor antibody titer was similar to previously published values for healthy ferrets.

CLINICAL RELEVANCE

Findings indicated that clinical and serologic remission can be achieved in ferrets with myasthenia gravis. However, owner willingness to provide extensive supportive care was vital to the outcome for this patient, as was the owner's decision to not euthanize the ferret despite an initial lack of response to treatment.

Full access
in Journal of the American Veterinary Medical Association

Abstract

Case Description—A 7-month-old neutered male ferret was evaluated for episodic pelvic limb weakness of 2 weeks' duration.

Clinical Findings—Neurologic examination revealed flaccid tetraparesis with decreased spinal reflexes suggestive of a neuromuscular disease. Results of hematologic and CSF analyses, thoracic radiography, and abdominal ultrasonography were unremarkable. Electrodiagnostic testing revealed subtle spontaneous activity localized to pelvic limb interosseous muscles, unremarkable motor nerve conduction velocities, and lower than typical compound muscle action potential (CMAP) amplitude for tibial nerve stimulation only. A severe decremental response of the CMAP was detected with repetitive nerve stimulation (45.5% at the third ulnar nerve). An esophagogram revealed mild megaesophagus. Intravenous neostigmine methylsulfate administration resulted in immediate resolution of muscle weakness. Cross-reacting anti-acetylcholine receptor (AChR) antibodies were detected in serum (0.35 nmol/L) by use of a canine- and feline-specific muscle extract. Clinical signs and ancillary test results were diagnostic of acquired myasthenia gravis.

Treatment and Outcome—Pyridostigmine bromide was administered (1 mg/kg [0.45 mg/lb], PO, q 8 h), resulting in complete remission of clinical signs. However, 1 month after the diagnosis, the ferret was euthanized because of recurrence of weakness despite anticholinesterase treatment.

Clinical Relevance—To the authors' knowledge, this is the first report of acquired myasthenia gravis in a ferret and the first identification of anti-AChR antibodies in this species. Autoimmune myasthenia gravis should be considered in ferrets when weakness and flaccid paresis suggest a neuromuscular disease. Electrodiagnostic testing, anticholinesterase challenge, and AChR antibody titer determination were helpful for diagnosis of this condition.

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in Journal of the American Veterinary Medical Association

Abstract

Case Description—A 4-year-old domestic shorthair cat was evaluated for a 1-week history of shifting limb lameness that progressed to tetraparesis.

Clinical Findings—Physical examination revealed generalized muscle atrophy and signs of discomfort when the muscles of the appendicular skeleton were palpated. Neurologic examination revealed diminished myotatic and withdrawal reflexes in all 4 limbs. Results of a CBC indicated mild neutrophilia, and serum biochemical analysis revealed mild hyperalbuminemia and high creatine kinase activity. The cat was anesthetized, and an electromyogram (EMG), CSF sample, and nerve and muscle biopsy specimens were obtained. The EMG revealed positive sharp waves and fibrillation potentials, CSF analysis revealed albuminocytologic dissociation, and histologic examination of muscle and nerve specimens revealed severe myositis and neuritis. Immune-mediated polymyositis and neuritis were suspected.

Treatment and Outcome—With physical therapy and long-term corticosteroid drug treatment, the cat recovered complete motor nerve function.

Clinical Relevance—The severity and rapid progression of clinical signs, combined with the EMG abnormalities and histologic findings, could have led to inappropriate euthanasia for this cat. Veterinarians should be aware that immune-mediated polymyositis and neuritis in cats can have an excellent prognosis with appropriate, long-term treatment.

Full access
in Journal of the American Veterinary Medical Association
in Journal of the American Veterinary Medical Association

Abstract

Objective—To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats.

Animals—53 specific pathogen-free black domestic shorthair cats.

Procedure—Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for ≤ 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats.

Results—After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet.

Conclusions and Clinical Relevance—Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function. ( Am J Vet Res 2004;65:671–680)

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in American Journal of Veterinary Research