Prince Robert of Luxembourg and Princess Julie of Nassau's youngest son, Prince Frederik, has passed away after a protracted struggle with POLG mitochondrial syndrome, an extremely uncommon genetic illness, at the age of 22.

In a statement posted on the website of the POLG Foundation—which Frederik established in 2022—his family confirmed Frederik's death in Paris on March 1, as The New York Post reported.

“One light was extinguished, but so many remain,” his father said in the statement.

POLG is reportedly a “genetic mitochondrial disorder that robs the body’s cells of energy, in turn causing progressive multiple organ dysfunction and failure,” according to the foundation’s website.

The Diagnosis

The family reported that Frederik was 14 years old when he was diagnosed with POLG.

Diagnosis might be challenging due to the disease's wide-ranging symptoms and its impact on multiple organ systems.

It was Rare Disease Day—an international awareness day for rare diseases—the day before the prince passed away. A n estimated 300 million people live with a rare disease at any given time.

“As is the case for 300 million people like Frederik worldwide, these diseases are usually hard to recognise even by physicians, and patients’ families may never know what they are suffering from as they may only be identified very late in their progression,” his father, Robert, said.

The Prognosis

At this time, there is neither a treatment nor a cure for POLG.

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

“Frederik and the POLG Foundation … are committed to finding therapies and a cure to save other patients from suffering what Frederik and our family have endured,” he added.

Despite his condition, Frederik is said to have “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,” Robert wrote.

“Though Prince Frederik always made it very clear that he did not want the dreadful disease to define him, he devoted himself to spreading awareness on the rare disease,” the family said.

Search for a Cure

The prince was said to have participated in medical trials “with the goal of finding treatments and, perhaps, ways of repurposing molecules to help patients with his condition.”

Robert, Frederik's father, is fifteenth in line of succession and is a first cousin of Grand Duke Henri, the present head of state of Luxembourg.