Congenital myasthenic syndrome (CMS) is an inherited Neuromuscular Disease affecting Labrador retrievers. Affected dogs typically present around 2-3 weeks of age with severe exercise-induced weakness of all four limbs leading to collapse. Affected dogs will have decreased reflexes in all limbs and a short-strided gait that becomes more pronounced with exercise. Dogs may be humanely euthanized at a young age due to disease severity. Treatments used for a similar, acquired form of the disease known as myasthenia gravis, are ineffective for CMS.