Centronuclear Myopathy (CNM) – Labrador Retriever

Puppies with CNM are born without symptoms, and during the first few weeks they appear normal. From the second month of life, however, differences become noticeable compared to their healthy littermates. Affected puppies develop muscle weakness and exercise intolerance, which worsen with stress or cold. For some dogs, even a one- to two-minute walk at their own pace can be too much. Muscle loss (atrophy) also occurs, most visibly in the thighs and in the masticatory muscles of the head (particularly the temporal muscle, located between the eye and ear). Due to this weakness, many affected dogs carry their heads low and develop a rounded (arched) back. In addition to these clinical signs, a veterinarian performing a neurological exam will often find that the knee-jerk reflex is absent. Treatment is not available.