NEUROMUSCULAR CASE OF THE MONTH – SEPTEMBER 2007

Myositis: A new problem in Hungarian Vizsla dogs
Contributed by Dr. G. Diane Shelton and Diane Addicott



An inflammatory myopathy (myositis) with clinical signs of atrophy of the masticatory muscles (see images below), pharyngeal dysphagia with excessive drooling and difficulty swallowing, and megaesophagus and regurgitation, has recently been identified in several young adult Hungarian Vizsla dogs from the UK (for information on the UK dogs go to http://vizslamyositis.blogspot.com/ and from the USA (Shelton, unpublished). Although atrophy of the masticatory muscles is a prominent clinical sign, generalized loss of muscle mass may be evident with exercise intolerance. The serum CK concentration, an indicator of muscle damage, is usually elevated. These cases should not be confused with masticatory muscle myositis, as clinical signs in Vizsla myositis involve more muscle groups than just the muscles of mastication, and the serum antibody titer against masticatory muscle type 2M fibers has been negative in affected dogs. The serum acetylcholine receptor antibody titers for myasthenia gravis have also been negative. Electrodiagnostic studies have shown generalized abnormalities of muscle with normal nerve function. Muscle biopsies are critical for confirmation of a diagnosis of myositis and for accurate classification of this disease. Many of the affected Vizsla dogs in the UK were related, suggesting a possible breed predisposition to this myopathy such as occurs in the Newfoundland breed (Evans et al J Vet Intern Med 2004;18:679-691). While the underlying cause of this inflammatory myopathy is not yet known, an immune-mediated disorder (polymyositis) is postulated, and the dogs are steroid responsive. We are interested in identifying additional affected dogs in both the UK (see website above for contact information) and in the USA (contact musclelab@ucsd.edu). Only with complete evaluations of these dogs can we learn more about this disabling and disfiguring condition, identify optimal treatments, and investigate possible inheritance patterns which would be helpful to breeders.

The Vizsla Club of America Welfare Foundation is conducting a 2008 Health Survey (http://ipgwcu.org/vizsla/). We encourage owners or veterinarians that are treating cases of this breed associated polymyositis, masticatory muscle myositis, or myasthenia gravis to complete the health survey. This will help us determine the incidence of these diseases in the Vizsla breed.  

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“Radio” Pre-Myositis

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“Radio” Post-Myositis

 

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“Jasper” Pre-Myositis

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“Jasper” Post-Myositis

 

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