Prince Frederik, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, died at age 22 on March 1 from the rare genetic condition POLG Mitochondrial disease.

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.

Prince Frederik, 22, was a founder and the creative director of a foundation that raised awareness of POLG disorder.