Endocarditis. The most common type of inflamed heart valve is due to infection, known as endocarditis. This is a life-threatening condition caused by germs, especially bacteria that attack heart valves causing holes, growths, thickening and scarring. This can lead to leaky valves. People with valve disease (except mild mitral valve prolapse without thickening or regurgitation) are at increased risk.
Rheumatic fever. Rheumatic fever is caused by an untreated bacterial infection (usually strep throat). Luckily, the introduction of antibiotics to treat this infection has dramatically reduced the numbers of this infection. The initial infection usually occurs in children, but the heart problems associated with the infection may not be seen until 20-40 years later. Mitral stenosis or regurgitation can occur.