A narrowing of the mitral valve, which controls blood flow from the heart's upper left chamber (the left atrium) to its lower left chamber (the left ventricle). May result from an inherited (congenital) problem or from rheumatic fever.
A disease, usually occurring in childhood, that may follow a streptococcal infection. Symptoms may include fever, sore or swollen joints, skin rash, involuntary muscle twitching, and development of nodules under the skin. If the infection involves the heart, scars may form on heart valves, and the heart's outer lining may be damaged