Prince Frederik of Luxembourg died at the age of 22 due to a rare mitochondrial condition called POLG disease— Newsweek has rounded up what you need to know about the illness. The European royal died in Paris on March 1, one day after "rare disease day," according to his father Prince Robert of Luxembourg's public announcement.

Prince Frederik, the son of Europe's Prince Robert of Luxembourg, has died from a rare genetic disease, his family announced.

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