Complications
Untreated group A strep infections can result in rheumatic fever and post-streptococcal glomerulonephritis (PSGN).
Rheumatic fever can develop about 18 days after a bout of strep throat and causes heart disease with or without joint pain. It can be followed months later by Sydenham chorea, a disorder in which the muscles of the torso, arms, and legs move involuntarily in a dancing and jerky manner.
PSGN is an inflammation of the kidneys that may follow an untreated strep throat but more often comes after a strep skin infection.
Both disorders are rarely seen in the United States because of prompt and effective treatment of most cases of strep throat.