[Granular media calcinosis of the aorta. Structural findings, historical review and pathogenetic significance].

Granular mediacalcinosis of the aorta seems to be a forgotten phenomenon that had been intensively investigated at the beginning of the past century. Without knowledge of this older literature we were, first of all, astonished to find in histological sections from aortic aneurysms, appearing "normal" in the H&E stain, severe calcifications of the media in von Kóssa and Alizarin red S stained sections. Therefore, 24 operation specimens of aneurysms were investigated with several morphological methods. In all cases, light microscopy exhibited granular medial calcification with a slight increase of the severity in specimens from older patients. Scanning electron microscopy on paraffin sections revealed calcified globules with diameters of about 1 micron localized between the elastic laminae. By transmission electron microscopy these calcospherites occupied the space between the elastic laminae. X-ray microanalysis exhibited high amounts of calcium and phosphorus and a smaller amount of magnesium. This atomic composition supports the findings of Reid and Andersen (69) indicating that these calcifications are due to the deposition of whitlockite. These morphological findings are supplemented by a review of the older literature. The biological significance of this calcification remains unknown. On the one hand, it may be responsible for the increasing stiffness of the aorta in older age groups--and, on the other hand, a pathogenetic role for the development of dissecting aneurysms cannot be excluded. This may be supported by the effect of beta-aminopropionitril in lathyric rats with destruction of the interlaminar fibers, described by Nakashima and Sueishi (65): it seems possible that a focal increased calcification in the human aorta may disturb the connection between the elastic laminae, thus, facilitating their separation.