A 68-year-old man developed progressive weakness over 4 weeks. He had difficulty rising from a low position, climbing stairs, and raising his arms overhead, particularly toward evenings. He had no pain, sensory, or bowel or bladder symptoms, and denied ptosis, diplopia, dysphagia, or dyspnea. He had mild unintentional weight loss but no fevers. His medical history revealed eczema and active smoking (50 pack-years). There was no family history of neuromuscular disorders.