Myotubular Myopathy 1 (Rottweiler type) is an inherited muscle disease affecting dogs. Affected puppies are typically normal at birth, but between 7 to 13 weeks of age they present with muscle weakness, decreased muscle mass, and exercise intolerance. Affected puppies have difficulty standing and holding their head up and their whiskers may be bent or crinkled. The disease rapidly progresses from generalized muscle weakness and frequent episodes of collapse to 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 and stiff gait. While the disease is not painful, affected dogs are often euthanized between 3 to 4 months of age due to the rapid and severe progression of the disease.