The events from Jehoram's reign that the Chronicler selected present a classic example of the consequences that follow departing from Yahweh. The king violated God's will by murdering his brothers (v. 4) and practicing idolatry (v. 6).
"Jehoram is the first king of the Davidic line of whom the Chronicler's judgment is totally negative."55
"There is both irony and retributive justice in that Jehoram sets in motion events that would ultimately lead to the near obliteration of his own line (22:10; 2 Kgs 11:1)."56
The retributions Yahweh brought for these sins were the rebellion of and invasion by his neighbors (vv. 8-10, 16-17), his own painful death (vv. 18-19), and death with no one's regret (v. 19).
"It cannot be said too often that the tracing of cause and effect which so typifies Chr. does not imply that all suffering is the result of specific sin. The central point here relates rather to the folly and wickedness of usurping the place of God. Jehoram did not merely aim to exercise authority. He sought to control destinies. The same urge is not absent from the twentieth century."57
Even though Jehoram apostatized largely through the influence of his wife and in-laws in Israel (v. 6), God did not cut off the Davidic line. This was because He had promised David He would never do that (v. 7).
It is significant that the prophet God sent to announce judgment on Jehoram was Elijah (v. 12). Elijah's ministry was to condemn Baalism in Israel, but God sent him to Jehoram because Jehoram shared the same guilt as the kings of Ahab's house. This is the only record we have of a prophet from the Northern Kingdom rebuking a king of the Southern Kingdom. All the other prophets God sent to the Davidic kings were from Judah.
"As with most illnesses mentioned in the Old Testament, we are left to conjecture about the clinically imprecise vocabulary. Ulcers, colitis, chronic diarrhea, and dysentery have been proposed."58
The reference to Jehoshaphat having been the king of Israel (v. 2) is not an error. As we have already noted, the Chronicler regarded Judah as the true Israel and sometimes referred to Judah as Israel (cf. 12:6; 23:2; et al.).
(NT only) to listen to the NET Bible 
