Two different pathogenetic pathways in lichen amyloidosus and macular amyloidosis

Area of Science:

• Dermatology
• Pathology
• Biochemistry

Background:

• Lichen amyloidosus (LA) and macular amyloidosis (MA) are characterized by amyloid deposits in the upper dermis.
• Previous research suggested an epidermal origin for amyloid, involving degenerating keratinocytes.
• The exact pathogenesis of amyloid formation in these conditions requires further elucidation.

Purpose of the Study:

• To investigate the pathogenetic pathway of amyloid formation in lichen amyloidosus (LA).
• To compare the proposed mechanism in LA with the established pathway in macular amyloidosis (MA).
• To explore potential differences in amyloid morphology and formation based on distinct pathogenetic mechanisms.

Main Methods:

• Electron microscopy was used to examine amyloid deposits in LA and MA.
• Comparative analysis of ultrastructural features of amyloid in both conditions.
• Histopathological examination of skin biopsies.

Main Results:

• Amyloid deposits in LA and MA are located in the upper papillary dermis.
• A previously proposed epidermal origin (degenerating keratinocytes) is considered plausible for MA.
• An alternative pathway is suggested for LA, where amyloid fibrils may form on the dermal surface of living basal keratinocytes.

Conclusions:

• The distinct morphology of amyloid in LA and MA might be due to partially different pathogenetic mechanisms.
• Amyloid formation in LA may involve basal keratinocytes, contrasting with MA's epidermal origin theory.
• Despite potential differences in formation, the amyloid in LA and MA could be chemically related.