Abstract
A 2-year-old male, intact Boxer was referred for chronic diarrhea, hyporexia, labored breathing, weakness and elevated creatine kinase, and alanine aminotransferase activities. Initial examination and diagnostics revealed a peripheral nervous system neurolocalization, atrial premature complexes, and generalized megaesophagus. Progressive worsening of the dog’s condition was noted after 36 h; the dog developed aspiration pneumonia, was febrile and oxygen dependent. The owners elected humane euthanasia. Immediately postmortem biopsies of the left cranial tibial and triceps muscles and the left peroneal nerve were obtained. Postmortem histology revealed concurrent myositis, myocarditis, endocarditis, and ganglioneuritis. Mixed mononuclear cell infiltrations and a distinct perifascicular pattern of muscle fiber atrophy was present in both muscles. This is a novel case of diffuse inflammatory myopathy with a distinct perifascicular pattern of atrophy in addition to endocarditis, myocarditis, and epicarditis.
Highlights
Inflammatory myopathies are relatively common in dogs and may be localized to specific muscle as in masticatory myositis, extraocular myositis, and glossitis, or be a generalized disorder including immune-mediated polymyositis (PM), dermatomyositis, infectious myositis, and as a paraneoplastic syndrome [1]
The myositis was pleocellular with an increased population of eosinophils
Due to the infiltration of scattered eosinophils in various soft tissues, sections of frozen heart, and skeletal muscle were tested for Neospora caninum using polymerase chain reaction (PCR) testing and were negative
Summary
Inflammatory myopathies are relatively common in dogs and may be localized to specific muscle as in masticatory myositis, extraocular myositis, and glossitis, or be a generalized disorder including immune-mediated polymyositis (PM), dermatomyositis, infectious myositis, and as a paraneoplastic syndrome [1]. We describe an unusual case of PM in a Boxer with concurrent megaesophagus, myocarditis, endocarditis, and ganglioneuritis. Perifascicular atrophy is the occurrence of small muscle fibers at the periphery of a fascicle that are atrophic with some fibers regenerating, and are thought to reflect ischemic changes secondary to disease of the vessels [6]. This pattern is found in most, but not all, cases of human dermatomyositis [6] but not in familial canine dermatomyositis [7]
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