We report the case of a 72-year-old man who had contracted acute paralytic poliomyelitis in his childhood. Thereafter, he had suffered from paresis involving the left lower limb, with no relapse or progression of the disease. He began noticing slowly progressive muscle weakness and atrophy in the upper and lower extremities in his 60s. At the age of 72, muscle weakness developed rapidly, and he demonstrated dyspnea on exertion and dysphagia. He died after about 14 years from the onset of muscle weakness symptoms. Autopsy findings demonstrated motoneuron loss and glial scars not only in the plaque-like lesions in the anterior horns, which were sequelae of old poliomyelitis, but also throughout the spine. No Bunina bodies, TDP-43, and ubiquitin inclusions were found. Post-polio syndrome is rarely fatal due to rapid progressive dyspnea and dysphagia. Thus, the pathological findings in the patient are considered to be related to the development of muscle weakness.