Carcinoid syndrome, systemic lupus erythematosous, rheumatoid arthritis, mucopolysaccharidosis, atrial myxoma, and congenital lesions may be rare causes of mitral stenosis. Two thirds of all patients with rheumatic mitral stenosis are female. The rheumatic valve lesion can result in stenosis, regurgitation, or both. Pure stenosis is more prevalent among young adults while older adults usually present with mixed lesions.
Pure insufficiency appears to be more frequent in early childhood.
Although the most damaging long term effects of rheumatic fever involve the endocardium, specifically the endocardium of the mitral valve, the myocardium and pericardium are also affected. The cross-sectional area of the open mitral orifice is at least 6cm2 in the normal adult heart. When the orifice is decreased to less than 2 - 2.5 cm2, the left atrial pressure becomes elevated. The elevated left atrial pressure is then transmitted to the pulmonary veins resulting in pulmonary edema. The sensation of shortness of breath resulting in the hallmark symptom of dyspnea on exertion are a result of the increase in pulmonary blood volume.