This 60-year old woman presented with pruritic, hyperkeratotic plaques on her back. The clinical differential diagnosis included lichen amyloidosis versus lichen simplex chronicus. Lichen amyloidosis belongs to the family of skin-limited amyloidoses which also includes macular amyloidosis and biphasic amyloidosis. The typical clinical presentation is that of severely pruritic papules and plaques on the shins or extensor surfaces of the arms of dark-colored individuals. The amyloid deposits are of keratin type (keratins 1, 5, 10, and 14) and are believed to originate from the epidermis, break through the basement membrane, and finally settle in the papillary dermis. Lichen amyloidosis is thought to result from repetitive scratching of an underlying, severely pruritic condition.
Higher power view demonstrates hyalinized amorphous material deposited within and expanding the papillary dermis, reducing the rete ridges into thin septae.