Abstract
The coronary arteries of young individuals ranging from fetuses to young adults were studied. Sclerotic lesions were not demonstrated in the coronary arteries of fetuses. In infants the early stages of arteriosclerosis were frequently present and consisted of rupture, degeneration and regeneration of the internal elastic membrane, deposition of mucopolysaccharide, and proliferation of endothelial cells and fibroblasts. These alterations were most prominent in infants of 3 to 4 months. In older individuals there was an apparent decrease in the rate of intimal fibrosis. The lesions of the coronary arteries of young individuals were identical with the early phases of arteriosclerosis in adults.