The son of Prince Robert of Luxembourg and Princess Julie of Nassau, Prince Frederik, has died in Paris the age of 22 due to a rare genetic disorder – POLG Mitochondrial disease.
Prince Robert announced his son’s death in an emotional message on the POLG Foundation website, founded by Frederik to help find treatments for POLG.
Frederik was diagnosed with POLG at age 14, the family said. Because the disease causes such a wide range of symptoms and affects many different organ systems, it can be difficult to diagnose.
“Frederik passed on March 1st 2025, in Paris France, the City of Lights. One light was extinguished, but so many remain,” Prince Robert wrote.
“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 added.
“He had barely been able to speak for several days, so the clarity of these words was as surprising as the weight of the moment was profound,” the prince said.
“He had already spoken all that was in his heart to his extraordinary mother, who had not left his side in 15 years,” Prince Robert wrote, referring to his wife.
What is POLG?
PolG disease is genetic condition that depletes the body’s cells of energy.
This in turn causes progressive multiple organ dysfunction and failure.
“One might compare it to having a faulty battery that never fully recharges and is in a constant state of depletion,” the POLG foundation explains online.
The condition affects mitochondria, the “powerhouse” of the cell which convert food into ATP, the primary energy our body uses to function.
Mitochondria contain their own DNA which requires a specific enzyme to replicate, found in host cell’s POLG and POLG2 genes. Mutations in these genes therefore impact the ability for mitochondria to replicate.
What are the symptoms?
Symptoms can start from early childhood to adulthood and can be mild to severe.
The most frequent symptoms include muscle weakness, ophthalmoplegia (weakness of paralysis of the eye), epilepsy and liver failure.
It can be very difficult to diagnose because it affects a wide variety of organs and has many symptoms.
There is currently no treatment or cure for POLG.
What did Frederik say about his condition?
Frederik was born with the mitochondrial disease and diagnosed at age 14 as his symptoms were increasingly noticeable.
The late 22-year-old previously spoke out about his genetic condition. Last year, he was featured in his organization’s short film, The POLG Foundation Film, which includes a scene of him watching videos from his childhood.
“When you’re a kid, you’ve got all these dreams, all these aspirations, these things you want to do. The possibilities are endless,” he said in a voiceover.
“I’m not sure I understood all the consequences of PolG when I first got diagnosed. It’s more subtle, where slowly, the world is getting smaller and smaller,” he added.
"In our family, there exists life before July 26th, 2016 and life after. On that date, our then-14-year-old son, Frederik, was diagnosed,” Frederik’s parents said.
Adolescent onset POLG is thought to be one of the most difficult forms of mitochondrial diseases, the foundation explains on its website.
“As an adolescent, when Frederik and others like him, should be riding the exciting hormonal rollercoaster of teenage life, among a myriad of other challenges, they are instead facing the possibility of losing their ability to walk, eat and see,” the foundation said.
“The worst thing is that they are informed that there are currently no effective treatments and no cure.”
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