What disease struck King Uzziah?

Answer: Leprosy

The LORD afflicted King Uzziah (Azariah) with leprosy until he died; he lived in a separate house while his son Jotham governed.

“And the LORD afflicted the king with leprosy until the day he died, so that he lived in a separate house while his son Jotham had charge of the palace and governed the people of the land.”— 2 Kings 15:5 (BSB)