Acquired myasthenia gravis and exfoliative dermatitis in a cat with suspect thymoma

Acquired myasthenia gravis and a cranial mediastinal mass were diagnosed in a domestic shorthair cat with dyspnea and generalized weakness. Based on thoracic radiographs and ultrasonography and biopsy of the mass a thymoma was suspected. After an initial clinical remission with medical therapy and before the scheduled thymectomy the cat had a recurrence of the clinical signs, developed exfoliative dermatitis and died. Myasthenia gravis and exfoliative dermatitis are uncommon paraneoplastic syndromes that are sometimes associated with thymoma.