Myopathy is any abnormality or disease of muscle tissue. It is characterized by progressive muscle degeneration due to dysfunction of muscle fibers. In myopathy, the muscle fibers do not function due to one of many reasons which result in generalized muscle weakness. In bpth black and yellow labrador retrievers, this condition is hereditary and is transferred by simple autosomal recessive mode of inheritence.
Onset of symptoms typically occur between the ages of three to four months. Common symptoms include
Downward flexion of head and neck
Abnormal joint posture
Excessive laying down (in some dogs)
Many of these symptoms worsen with cold weather, excitement and exercise. Improvement is seen once the dog is allowed to rest.