Paradoxical Pseudomyotonia

Affected dogs present within the first two years of age (generally at approximately 6 months) with episodes of exercise-caused myotonia. These episodes result in generalized muscle stiffness and may cause affected dogs to walk strangely (described sometimes as “running in a computer game”), or get stuck while climbing stairs or jumping. In more severe cases, the dog may collapse and have difficulty breathing. Episodes typically last for several seconds to under one minute, and resolve with rest. They are caused by strenuous exercise, and may be worsened by stress, excitement, and particularly high or low temperatures.