Prince Frederik of Luxembourg died after years of being diagnosed with a rare mitochondrial disease called PolG.

Prince Frederik of Luxembourg, who died at 22, spoke about the rare genetic disorder he navigated in a video released by The PolG Foundation he founded.

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.