Elastic fiber abnormalities associated with a leaflet perforation in floppy mitral valve.

The alterations observed in the elastic fibers of the perforated floppy mitral valve of a 68-year-old man are described. The patient had not history of infective endocarditis and no stigmata of Marfan syndrome or Ehlers-Danlos syndrome. Ultrastructurally, the elastic fibers in the area of the perforation showed unique, round-shaped expansion of the amorphous components, which lacked associated microfibrils. These features resembled those of the elastic fibers in animals treated with beta-aminopropionitrile, an inhibitor of lysyl oxidase. Aggregations of microfibrils without amorphous components were also observed. These abnormalities are considered to be related to the pathogenesis of the perforation in this valve.