Prince Frederik of Luxembourg, the 22-year-old son of Prince Robert of Luxembourg, has died after a lifelong battle with a rare genetic disorder known as POLG mitochondrial disease. The young royal passed away on March 1, 2025, in Paris, France, just one day after Rare Disease Day.

Prince Robert, who is the first cousin of Grand Duke Henri, the current ruler of Luxembourg, announced the sad news in a heartfelt blog post on the website of The POLG Foundation, a nonprofit organization founded by Frederik following his diagnosis in 2016.

“It is with a very heavy heart that my wife and I would like to inform you of the passing of our son, The POLG Foundation Founder and Creative Director, Frederik,” began the message from Prince Robert.

Frederik was diagnosed with POLG mitochondrial disease at the age of 14 when his symptoms became more apparent. Despite this diagnosis, he showed remarkable resilience and became a dedicated advocate for raising awareness and finding treatments for the condition.

POLG mitochondrial disease is a genetic disorder that robs the body’s cells of energy, causing progressive multiple organ dysfunction and failure. The disease affects the body’s mitochondria, which are responsible for producing energy in cells, and can impact various organs including the brain, nerves, muscles, and liver.

According to the POLG Foundation’s website, the disease is estimated to affect one in every 500 people and is considered the second most commonly diagnosed serious genetic disease after cystic fibrosis. Despite its prevalence, there is currently no known cure or effective treatment for POLG mitochondrial disorders.

In 2022, Frederik co-founded The POLG Foundation to support research into effective treatments and ultimately find a cure for POLG mitochondrial disorders. Under his leadership as Creative Director, the foundation has provided $3.6 million in funding for research projects and has partnered with Columbia University to develop tools to assess disease progression.

Frederik’s own DNA was used to advance scientific understanding of POLG and mitochondrial research, contributing to knowledge that may have implications for other diseases such as cancer and neurodegenerative disorders.

In his blog post, Prince Robert shared touching details about his son’s final moments, describing how Frederik found the strength to say goodbye to his family members.

“Last Friday, February 28th, on ‘Rare Disease Day’, our beloved son called us in to his room to speak to him for one last time,” Prince Robert recounted. He noted that Frederik had already spoken all that was in his heart to his mother, Princess Julie, “who had not left his side in 15 years.”

Beyond his work with the foundation, Prince Robert described his son as having exceptional social skills, humor, and determination. He characterized Frederik as a “Superhero” not only for their family but for many others affected by POLG around the world.

Despite the challenges he faced throughout his life, Frederik maintained a positive attitude and was known for his sense of justice and compassion.

Frederik is survived by his parents, Prince Robert and Princess Julie, as well as his siblings, Prince Alexander and Princess Charlotte, with whom he shared emotional goodbyes before his passing.

Prince Robert expressed that even after Frederik’s passing, his mission is not complete. The family plans to continue the work of The POLG Foundation to find a cure for POLG mitochondrial disease, with the hope of saving other patients from suffering the same fate as Frederik.

Research on POLG disease has broader implications, potentially informing the development of treatments for a variety of other diseases, including Alzheimer’s, Parkinson’s, diabetes, heart diseases, depression, and some cancers.

Medical experts note that POLG-related disorders comprise a spectrum of overlapping phenotypes with onset ranging from infancy to late adulthood. The most severe forms, such as Alpers-Huttenlocher syndrome, typically manifest in childhood, while milder forms may not be diagnosed until adulthood.

The early symptoms of POLG mitochondrial disease can be difficult to detect, contributing to challenges in diagnosis and treatment. Patients with the condition often face an uncertain future as they witness their own progressive loss of function.

For those affected by POLG, the work initiated by Prince Frederik through his foundation offers hope for future treatments and potentially a cure, ensuring that his legacy extends far beyond his brief 22 years of life.