The beloved royal died on March 1 from POLG Mitochondrial disease — a rare genetic disorder that affects approximately one in 5,000 people.

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

P rince Frederik of Luxembourg, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, died in Paris at age 22 on March 1—a day after Rare Disease Day—of a rare genetic disease known as POLG.