The reason it's interesting is that the star appears to contain a variety of short-lived isotopes, not just of plutonium: e.g. promethium-145, with a half-life of just under 18 years.

Some as-yet unidentified process is replenishing the star's isotopes. An idea I've seen[1] is that the radiation from its neutron star sibling, invisible to us, is powerful enough to trigger nuclear reactions in the star's ionosphere.

1. "A hypothesis for explaining the origin of Przybylski’s star (HD 101065)" http://link.springer.com/article/10.1007/s11963-008-1005-7