The precise cause and pathogenesis of atheroma formation remains unknown.
A. Current Pathogenic Theories
1. The Initial Lesion
The initial lesion is a small focus of injury of the intima caused by increased turbulence of blood at special arterial sites such as the orifice of branches — particularly that of the aorta as mentioned above — bifurcations, and curvatures that cause characteristic alterations in blood flow. This small area of injury incites a unique protective, nonspecific inflammatory response, but nature’s healing has to contend with further turbulent blood flow and further injury to the intima.
2. The Accumulation of Lipoprotein Particles
From observations in young adults dying of trauma and in rabbits fed a diet high in cholesterol and saturated fat, the accumulation of small lipoprotein particles in the intima has been noted to be one of the first ultrastructural alterations. This observation was noted in the 1950s and still finds space in major cardiology textbooks printed in 2002. The search of a 1958 Muir’s textbook of pathology, provides similar lines: ‘‘fatty degeneration usually occurs in the intima. On microscopic examination they are found to be due chiefly to fatty material in stellate cells of the intima and macrophages, and to a certain extent in the endothelial cells. This fatty deposit is cholesterol and glycerol fat. Such patches have been found in children dying acutely of trauma. They indicate that fat is prone to accumulate within the intimal cells but the reason for this is obscure.’’ It appears that much remains to be clarified regarding the pathogenesis of atheroma formation.

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