A 9-year-old Cairn Terrier was presented for a right thoracic limb lameness of 3-month duration resistant to anti-inflammatory pain treatment. Blood chemistry revealed a highly elevated creatine kinase activity. An orthopedic or vascular etiology of the lameness was excluded by radiographs, computed tomography, and magnetic resonance imaging. Further workup for a neurologic or muscular etiology by electromyography, nerve conduction velocity measurement, and histology of muscle as well as nerve biopsies identified the cause of the lameness. Histology revealed a pyogranulomatous, necrotizing myositis with parasites of the species . Furthermore different developmental stages of fungi were detected which were identified as sp. Treatment with albendazole and itraconazole significantly improved the patient's clinical signs.