Symptomatic tongue atrophy due to atypical polymyositis in a Pembroke Welsh Corgi

A three-year-old, 7.3-kg, female Pembroke Welsh Corgi exhibited symptomatic tongue atrophy, crinkling of the tip of the tongue, dysphagia and excessive salivation. Neurological examination suggested multiple cranial neuropathy, but polymyositis was diagnosed by magnetic resonance imaging and muscle biopsy. The dog did not respond to prednisolone treatment and died from aspiration pneumonia 22 months after the first presentation. Post-mortem histopathological examination of the tongue revealed marked myofiber loss and fibrosis with multifocal infiltration of mixed mononuclear cells. Similar findings were also observed in the masticatory muscles and quadriceps without abnormality of peripheral nerves or evidence of infection. Symptomatic tongue atrophy occurring in the course of polymyositis has not been reported previously in dogs.