Prince Frederik of Luxembourg, the youngest son of Prince Robert and Princess Julie, died from a rare genetic condition called POLG Mitochondrial disease. Prince Robert referred to his son as the family’s \”Superhero,\” and he highlighted the many achievements of the POLG Foundation, which Frederik helped found. Prince Frederik had POLG mitochondrial disease from birth, his father claimed that his symptoms did not become apparent until he was 14 years old. There is currently no cure for the ailment, which mostly affects the liver, muscles, nerves, brain, and other organs and can also impair vision, according to the U.S. Mitochondrian Disease Foundation states that mutations in thePOLG gene are the cause of mitochondrial ailment POLG disease. The foundation aims to support research and find a cure for POLG condition and Frederik established the foundation to help fund research. The cause of the illness is unknown, but there is no known cure for it, the foundation says.