He died on March 1 in Paris, his family announced the news through the POLG Foundation website, which Frederik had founded in 2022.

“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,” wrote his father, Prince Robert of Luxembourg.

POLG is a genetic mitochondrial disorder that affects the body’s cells, depriving them of energy and leading to progressive organ dysfunction and failure. Currently, no cure or effective treatment exists. The POLG Foundation has been dedicated to finding therapies and cures, with Frederik himself being a driving force behind the effort.

Prince Frederik was diagnosed with the disease at the age of 14. His family explained that the disease often goes unrecognized, with patients typically diagnosed only in the later stages.

“One might compare it to having a faulty battery that never fully recharges, is in a constant state of depletion and eventually loses power,” Prince Robert wrote.

Despite the challenges posed by his diagnosis, Frederik maintained an extraordinary perspective on his condition.

The prince found the strength to say goodbye to his loved ones in person, his father said.

“Frederik found the strength and the courage to say goodbye to each of us in turn–his brother, Alexander; his sister, Charlotte; me; his three cousins, Charly, Louis, and Donall; his brother-in-law, Mansour; and finally, his Aunt Charlotte and Uncle Mark,” Prince Robert wrote.

In his tribute, Prince Robert described Frederik as “disciplined and organized beyond belief,” recalling that the day before his death, his “Italian Duolingo and exercise alarm went off like any other day.”

The prince had never wanted his disease to define him, remaining deeply committed to raising awareness of POLG and its effects. He even participated in medical trials in hopes of advancing treatments.

“Though he always made it very clear that he did not want this dreadful disease to define him, he nonetheless immediately identified with and helped define the mission of The POLG Foundation,” the family’s statement read.

“Frederik passed on March 1st 2025, in Paris France, the City of Lights. One light was extinguished, but so many remain,” the family wrote.

Prince Frederik was the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau. Prince Robert is the paternal first cousin of Henri, the reigning Grand Duke of Luxembourg. As of Nov. 2024, Prince Robert is 15th in line to the Luxembourg throne.