Macular and lichenoid amyloidosis: a possible secretory product of stimulated basal keratinocytes. An ultrastructural study.

This study examined the histogenic pathways of amyloid formation in skin-limited amyloidosis. Skin biopsies taken from 10 cases of macular or lichenoid amyloidosis were studied with the light and electron microscope. Keratinocytes with filamentous degeneration were frequently encountered. They were normally eliminated either transepidermally through the surface or by macrophages at the dermoepidermal junction. Only occasionally was amyloid deposition observed to be associated with apoptotic keratinocytes undergoing filamentous change. On the other hand, small aggregates of amyloid were frequently observed at the dermoepidermal junction closely applied to healthy non-degenerate basal keratinocytes. The early appearance of amyloid at the dermoepidermal junction, its pattern of distribution and its intimate association with overlying active basal keratinocytes suggest that these fine, straight, interlacing fibrils may be a secretory product of stimulated basal keratinocytes.