The Comparative Neuromuscular Laboratory (CNL), established in 1990 at the University of California San Diego (http://vetneuromuscular.ucsd.edu), is a one of a kind international reference center for the pathologic diagnosis of spontaneous neuromuscular diseases in companion animals. The specific aim of this study is to identify a canine or feline model of dysferlin deficient muscular dystrophy by screening archived and newly received fresh frozen muscle biopsy specimens utilizing established immunoblotting and immunofluorescence methods. Once a specific breed or family of dogs is identified with dysferlin deficient muscular dystrophy, we will help other investigators establish such colonies of dogs for further investigations and testing new therapies.