Prince Frederik of Luxembourg, the youngest son of Prince Robert of Luxembourg and Princess Julie of Nassau, has died after a lifelong battle with a rare genetic disorder known as POLG mitochondrial disease.

Commissioned by Frederik’s mother, Princess Julia of Nassau, to helm an educational short film about the disease with Frederik at its center, director Mei Fa Tan said she was left “inspired” by the prince but also found it “painful to watch” him struggle with his health.

POLG-related diseases disrupt the function of the mitochondria, or "powerhouses" of the cell — starving them of energy.