Abstract
An 11-year-old female mix-breed dog was presented with a complaint of walking difficulty. A tentative diagnosis of acquired myasthenia gravis associated with thymoma was made by clinical signs, edrophonium test, radiographs and cytology. The clinical signs were controled well with pyridostigmine bromide and predonisolone therapy, but the dog suddenly died 4.5 months after presentation. Histopathology of the mediastinum mass was consistent with thymoma and multiple thymic cysts. In this case, diminution of the mass was observed without specific treatment for thymoma.
