and Relevance: This case is the first instance of using tracheal stenting to effectively manage tracheal stenosis in a cat, successfully resolving a respiratory emergency, and ensuring long-term care.

and Relevance: This case is the first instance of using tracheal stenting to effectively manage tracheal stenosis in a cat, successfully resolving a respiratory emergency, and ensuring long-term care.

and Relevance: This case is the first instance of using tracheal stenting to effectively manage tracheal stenosis in a cat, successfully resolving a respiratory emergency, and ensuring long-term care.

and Relevance: This case is the first instance of using tracheal stenting to effectively manage tracheal stenosis in a cat, successfully resolving a respiratory emergency, and ensuring long-term care.

Idiopathic polymyositis and masticatory myositis are autoimmune inflammatory myopathies seen in dogs. Here we report a case involving an 11-year-old spayed female mixed-breed dog with suspected masticatory myositis that was later confirmed to be idiopathic polymyositis. The dog presented with lethargy and reluctance to walk. Blood examination indicated markedly elevated creatine kinase and C-reactive protein levels. The owners were reluctant to proceed with advanced tests; however, the dog developed new clinical signs, including trismus. T2-weighted magnetic resonance imaging revealed hyperintensities in multiple muscle groups, with the most pronounced changes occurring in the masticatory muscles. During the waiting period for the results of serology for circulating autoantibodies against type 2M myofibers, oclacitinib was administered and slightly restored vitality and appetite. The antibody test result was negative, and histopathological examination of the temporalis muscle revealed severe inflammatory myopathy with fibroplasia. Although masticatory myositis was initially suspected on the basis of the MRI findings and the presence of trismus, the final diagnosis based on the overall clinical course and diagnostic test results was idiopathic polymyositis. Immunosuppressive treatment with prednisolone and mycophenolate mofetil substantially improved the clinical condition. The findings from this case suggest that, even in cases of idiopathic polymyositis exhibiting only nonspecific clinical signs, accurate diagnosis and timely treatment are essential to achieve satisfactory clinical outcomes.