A 36-year-old woman was concerned about being affected with a disease that ran in the family in an autosomal dominant (AD) manner. A few years before presentation, she noticed difficulty when walking in the mountains and this had gradually progressed to problems climbing stairs and an inability to run. She also noted that she could no longer lift her head when in supine position. Her mother had died of this disease in her early forties. She mentioned that many affected family members had been diagnosed with cardiac problems in addition to muscle weakness. Some were treated with an implantable cardioverter defibrillator. In elderly family members, cardiac enlargement was not uncommon.