Albert Barnes Commentary 2 Chronicles 26:20

"And Azariah the chief priest, and all the priests, looked upon him, and, behold, he was leprous in his forehead, and they thrust him out quickly from thence; yea, himself hasted also to go out, because Jehovah had smitten him." — 2 Chronicles 26:20 (ASV)

Death was decreed by the Law against those who usurped the office of the priest, and death had been the actual punishment of Korah and his company. Uzziah feared that he too would face the ultimate penalty, and therefore he hastened to leave the sacred building where his mere presence was a capital crime.