Albert Barnes Commentary 2 Kings 15:5

"And Jehovah smote the king, so that he was a leper unto the day of his death, and dwelt in a separate house. And Jotham the king`s son was over the household, judging the people of the land." — 2 Kings 15:5 (ASV)

The Lord smote the king, so that he was a leper - The circumstances under which this terrible affliction befell one of the greatest of the Jewish kings are given at some length by the author of Chronicles. This author supplies us with a fairly full account of this important reign, which the writer of Kings dismisses in half a dozen verses.

A several house - This means "a house of liberation" or "freedom." The Law required that lepers live apart from other people. Jotham became regent in his father's place and served as judge (see the note on 1 Kings 3:9) from the time his father became a leper.