A suspected case of unilateral extraocular polymyositis in a dog: diagnosis, advanced imaging features and therapeutic response

Abstract Extraocular polymyositis (EOM) is a rare immune‐mediated condition in dogs, which affects all the extraocular muscles and has been exclusively described to manifest bilaterally. This case report describes a 1‐year‐old, male, entire miniature dachshund that presented with a sudden onset, moderate right‐sided exophthalmos without protrusion of the nictitating membrane. Head computed tomography and ocular ultrasound demonstrated findings that were reminiscent of EOM. The dog was treated with an anti‐inflammatory dose of oral corticosteroids and amoxicillin/clavulanic acid. Rapid clinical improvement was observed, prompting an increase to an immunosuppressive dose of oral corticosteroids, which were tapered over 24 weeks. The patient showed complete recovery with no relapse at the 376‐day follow‐up. To the authors’ knowledge, this is the first documented case of presumed unilateral EOM in a dog.