Paradoxical pseudomyotonia (PP)

A genetic variant of the SLC7A10 gene has been found to be a candidate causative variant for paradoxical pseudomyotonia (PP) in the English Cocker Spaniel and English Springer Spaniel breeds. The disease can be characterized by exercise-induced episodes of myotonic-like muscle stiffness with variable severity. The episodes are in most cases non-painful and usually a spontaneous episode resolution within 45 seconds can be observed. However, in severe cases, dogs can also develop life-threatening episodes of apnoea and cyanosis. Moreover, exposure to cold or heat decreases the amount of exertion necessary to induce myotonia and weakness. First symptoms can be seen between 3 and 24 months of age, with no progression of the episodes. Haematological tests and urinalysis of affected dogs are unremarkable and the episodes are electrically silent on EMG. Clinical signs of mildly affected dogs can be decreased or prevented by avoiding triggers. In severally affected dogs with episodes of apnoea and cyanosis, medical treatment is effective in decreasing the severity and frequency of episodes.