Page 1246 - Veterinary Immunology, 10th Edition

protein-C found only in masticatory muscle fibers. Animals present
VetBooks.ir with pain and atrophy or swelling of the masticatory muscles

resulting in difficulty in opening (trismus) or closing the jaw.
Affected animals may also develop conjunctivitis or exophthalmos.

Histology of affected muscles shows inflammatory or degenerative
lesions affecting the M2 myofibrils. Myositis with lymphocytes and
plasma cells predominates, and some lesions may contain many
eosinophils. Myofiber atrophy, perimysial or endomysial fibrosis,

and muscle fiber necrosis are consistent features. Immunoglobulins
may be detected in biopsy specimens of affected muscles, and
circulating antibodies to the M2 myofibrils have been demonstrated
by an immunoperoxidase assay. Corticosteroids such as prednisone

are used for treatment, but the prognosis is guarded. Cavalier King
Charles Spaniels may be predisposed to this disease.

Canine Cardiomyopathy

English Cocker Spaniels may develop a cardiomyopathy with
antinuclear and antimitochondrial autoantibodies and reduced
serum IgA levels. It is associated with a specific C4 allotype (C4-4).
The autoantigen has not been identified, but in humans similar
cardiomyopathies are due to autoantibodies directed against the

adenine nucleotide translocator of mitochondria.

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