Prince Robert of Luxembourg and Princess Julie of Nassau have announced that their son, Prince Frederik, has died at 22.

The prince had PolG disease, a genetic mitochondrial disorder that prevents the body's cells from producing adequate energy.

Prince Frederik, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, has died. He was 22. Frederik ...

Prince Robert of Luxembourg, through the family's foundation. "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 ...

Frederik de Nassau died in Paris on March 1, a day after internationally recognized Rare Disease Day, which takes place on the last day of February, Prince Robert of Luxembourg said in a statement ...