Myopathy is a group of disorders of the muscle tissue that includes fibromyalgia, muscular dystrophy and myositis. Inherited myopathy of Great Danes (formerly called central core myopathy) is a congenital condition of the heart muscle characterized by weakness and delayed development. The disease is termed for the presence of cores on muscle biopsies. Cores are condensations of myofibrils and myofibrillar material in the central portion of each muscle fiber. If the cores appear large, the name central core myopathy is used; if there are multiple small cores, the term multiminicore myopathy is used. In young Great Danes onset of clinical signs is usually before one year of age and both sexes are affected.
Similar disease termed centronuclear myopathy (originally called hereditary Labrador retriever myopathy) has been reported in the Labrador Retriever breed. Affected puppies appear normal at birth. Muscular weakness, exercise intolerance, an awkward gait, and muscle wasting become apparent by 3 to 5 months, with a few puppies showing signs at 6 to 8 weeks. Severely affected dogs show a low head carriage and stilted gait. Clinical signs are worse with exercise, stress, or cold temperatures. No treatment is available.
Clinical signs are characterised by exercise intolerance, muscle wasting, abnormal posture, and an exercise-induced tremor which develop between 6 and 19 months of age. Male and female dogs with a fawn or brindle coat can be affected, and profound muscle weakness without myalgia has been reported.3 Although most affected dogs have a severe form of the disease, some animals may have a less pronounced form and survive into adulthood with an acceptable quality of life. The severity of signs and the speed of progression are variable, even within litters, with a few dogs becoming totally debilitated within 2 months and most affected dogs being euthanized within 1 year of diagnosis.3
- Lujan Feliu-Pascual A, Shelton GD, Targett MP, Long SN, Comerford EJ, McMillan C, Davies D, Rusbridge C, Mellor D, Chang KC, Anderson TJ. Inherited myopathy of great Danes
- Jan Stephen Tecklin. Pediatric Physical Therapy.
- A possible new inherited myopathy in a young Labrador retriever