Elastic tissue in pseudoxanthoma elasticum. Ultrastructural study of endocardial lesions.

A 56-year-old woman had pseudoxanthoma elasticum (PXE). Ultrastructural findings in the endocardium showed increased collagenogenesis and elastogenesis. The newly formed elastic fibers appeared morphologically normal, but showed a notable propensity to become calcified. The internal structure of the calcified areas was essentially similar to that of the adjacent uninvolved portions of the elastic fibers. Some of the heavily calcified fibers showed loss of internal structure and fragmentation. These findings support the concept that in PXE, calcification involves morphologically unaltered elastic fibers that subsequently may undergo secondary degenerative changes, such as loss of internal structure and fragmentation.