Rheumatic heart disease

The precise cause of rheumatic fever is unknown. However, there is much evidence that rheumatic fever is endocardium with group a hemolytic streptococci, probably on the basis of tissue allergy. There is no diagnostic laboratory test which is specific for the disease. Other factors include. Rheumatic fever is essentially a disease of temperate climates. It is much less common in the tropics. Rheumatic fever tends to occur in families, but this may be due to environment rather than heredity. Rheumatic fever commonly affects the lower income groups and town dwellers. Poor housing and overcrowding are important factors. The disease is often preceded by tonsillitis or pharyngitis one to three weeks before. The fibrous tissues of the body are involved. Joints, muscles, tendons, heart valves, subcutaneous tissues and blood vessels are all affected. In the educative stage there is hyperaemia, oedema of the collagen tissue and infiltration with leucocytes. The hallmark of rheumatic fever is the Aschoff nodule, which may be found in the interstitial tissues of any part of the heart, most frequently under the endocardium and in close relation to small blood vessels. Its microscopic appearance is that of a central area of necrosis surrounded by small round cells, histiocytes and giant cells. The lesions of rheumatic fever never suppurate.