Immunofluorescence and histochemical studies of localized cutaneous amyloidosis.

Lichen amyloidosus (LA) and macular amyloidosis (MA) are two forms of localized cutaneous amyloidosis in which the amyloid occurs as larger and smaller deposits respectively in the papillary dermis. The histogenesis of the amyloid of these conditions is unknown. By using an indirect immunofluorescence technique we showed that LA and MA do not react with antibodies against different previously characterized amyloid fibril proteins. These results indicate that the amyloid of LA and MA is different from other known types of amyloid. Protein AP, which was demonstrated in amyloid of MA and LA, is known to be present in all forms of amyloid and is of unknown significance. Antiserum against keratin did not react with the larger homogeneous amyloid bodies, but showed a weak reaction with some small deposits. Histochemical staining failed to show keratin in any of the tissues containing LA or MA.