I.I.4 Autoimmune muscle diseases in dogs and cats: Spontaneous models for evaluation of therapies?

Abstract

Spontaneously occurring autoimmune muscle diseases such as polymyositis (PM) and myasthenia gravis (MG) commonly affect dogs and to a lesser extent cats. A typical myopathic clinical phenotype including weakness, muscle atrophy and stiffness occurs in PM, and focal or generalized muscle weakness without atrophy occurs in MG. As in humans, diagnosis of PM is confirmed by muscle biopsies and immunophenotyping of cellular infiltrates, and of MG by a positive acetylcholine receptor antibody titer. Species-specific features of MG include frequent spontaneous immune remissions in the dog and a high incidence of thymoma associated MG in cats. Dermatomyositis in dogs is breed-associated and infrequently diagnosed. Most recently, a myopathy similar to spontaneous inclusion body myositis (sIBM) was identified in the dog recapitulating both the degenerative and inflammatory aspects of the human disease. Focal forms of immune-mediated myositis also occur in dogs including the apparently species-specific masticatory muscle myositis with muscle specific autoantibodies, and focal forms limited to other muscle groups. As rodent models have been largely unsuccessful in translation of new therapies for muscle diseases to human patients, large animal models of human muscle diseases are growing in importance and may be more clinically relevant. As autoimmune muscle diseases in large animals become better described and classified, these models of immune-mediated muscle disease will take a prominent role for therapeutic trials alongside the well established models of canine dystrophin deficient muscular dystrophy, centronuclear myopathy and myotubular myopathy.