Myotubular Myopathy is an inherited muscle disease affecting Labrador Retrievers. Affected puppies are typically normal at birth, but between 7 and 19 weeks of age they present with muscle weakness especially in the hind limbs, decreased muscle mass, a hoarse bark and difficulty eating. Puppies are smaller than littermates, walk with a short, choppy gait and often fall over. The disease rapidly progresses from generalized muscle weakness and frequent episodes of collapse to a complete inability to stand or even raise their heads within 4 weeks of initial presentation. Dogs that are able to stand have an arched back and neck. While the disease is not painful, affected dogs are often euthanized between 3 and 6 months of age due to the rapid and severe progression of the disease.