"Osmiophilic elastolysis" of peripheral organ arteries in patients with Marfan's syndrome

Electron microscopic examinations were performed on systemic muscle-type arteries from two teen-age girls with Marfan's syndrome. In the peripheral organ arteries, the internal elastic lamella revealed a feature tentatively termed "osmiophilic elastolysis". The lytic changes appeared segmentally in the form of electron-dense fragments, and were partly absorbed. Regenerated elastin had a normal structure and surrounded the elastolytic lesions. The same changes were observed in the newly formed small areas of elastin in the thickened intima. The remaining elastic lamella in the affected region contained numerous fine electron-dense granules. Intercellular substances, including collagen fibrils and proteoglycan, other than elastic fibers, were increased secondarily in the elastolytic lesions without any evidence of ultrastructural abnormality. Medical smooth muscle cells making contact with the elastolytic lesions were necrosed and absorbed, and smooth muscle cells in a state of synthesis were increased in the adjacent areas. Abnormal elastogenesis, which showed no remarkable changes macroscopically or light microscopically, was systemic but segmental in the peripheral organ arteries, and regeneration of the structurally normal elastin was concurrent with elastolysis. These events were diagnostic for Marfan's syndrome, and cannot be explained by the conventional theory of elastogenetic enzymic deficiency.