Dystrophy-like Myopathies

Numerous examples of progressive myopathies have been described in animals; many are heritable, and many resemble various types of muscular dystrophy in humans. Affected muscles have a variety of degenerative and atrophic changes. In Meuse-Rhine-Yssel cattle of Holland, a progressive fatal myopathy of the diaphragm and intercostal muscles has been described. Another dystrophy in cattle is weaver syndrome in Brown Swiss. Hyperplasia, commonly called double muscling ( Double Muscling), is a congenital myopathy found in some European breeds of cattle. Progressive myopathies have been reported in Merino sheep in Australia (an inherited autosomal recessive), in Pietrain pigs (Pietrain creeper syndrome), and in dogs, cats, chickens, turkeys, and mink. Inherited muscular dystrophy of mice and hamsters has been studied extensively; the hamsters have severe myocardial lesions and serve as a model for studies of cardiomyopathy.

Several types of muscular dystrophy are seen in dogs. An X-linked Duchenne-like muscular dystrophy is reported in Golden Retrievers in the USA and in Irish Terriers in Europe. Affected dogs, generally males, develop progressive muscular weakness, dysphagia, stiffness of gait, and muscular atrophy. Microscopically, the distinctive alteration is lack of dystrophia, a protein concentrated in the sarcolemma and essential for normal membrane function. Some dogs die with accompanying cardiomyopathy. A similar X-linked dystrophy with a lack of dystrophia is described in cats. A second type of dystrophy involves Labrador Retrievers in North America, Europe, and Australia. Clinical signs, which include stiffness, exercise intolerance, and muscular atrophy, develop by 6 mo of age. Autosomal recessive inheritance is implicated. A further dystrophy was described in dysphagic Bouviers in Europe.