Presence of basal lamina-like substance with anchoring fibrils within the amyloid deposits of primary localized cutaneous amyloidosis.

The dermal-epidermal (DE) junction areas of skin specimens obtained from 16 patients with either lichen amyloidosis or macular amyloidosis were studied. In the dermal papillae where amyloid was deposited, elastic fibers frequently were absent, but periodic acid-Schiff reaction after diastase digestion was homogenously positive. Ultrastructural studies revealed that a basal lamina-like substance with anchoring fibrils was present between and within amyloid deposits. By indirect immunofluorescence technique using an anti-basement membrane zone antiserum obtained from a patient with bullous pemphigoid, specific linear fluorescence occurred at the DE junction, and in a reticular pattern in dermal papillae. It seemed that apoptotic keratinocytes of the epidermis brought down basal lamina and fine fibrous components attached to it when these cells dropped down to the papillary dermis and became the source of amyloid. These findings support the hypothesis that epidermal keratinocyte degeneration plays an important role in the histogenesis of cutaneous amyloidoses.