Morphologic Study of “Cloudy Thickening” of Human Aortas as an Initial Change of Atherosclerosis

Abstract

The authors call attention to the existence of “cloudy thickening” as an initial change of human atheromatous plaque.
Macroscopically, the lesions are gray, opaque and lack of distinct borderline against unaffected intimal surface. They may be circumscribed round or considerably elongated along the long axis of vessels.
Microscopically, intimal edema is noticed and extracellular linear lipid is present along the internal elastic lamina.
Electron microscopic examination reveals extracellular deposits of cellular debris (probably originated from imigrated mononuclear cells or other intimal cells) in the same position to that of lipid.
Irreversible changing of cloudy thickening might depend on the amount of extracellular deposits and the increase of endothelial permeability.
Fibrin deposition and its organization would be the most important factor when the lesion progresses to the severer atherosclerotic change.
Estimation of Gore-Tejada's atherosclerotic index of human aortas performed by Mae supports the significancy of the cloudy thickening rather than that of the fatty streak or patch in the problem of atherogenesis.