Biphasic amyloidosis arising from friction melanosis.

A 40-year-old woman who had used nylon towels in the bath for about 10 years noticed hyperpigmentation on the prominent regions over the bones of the trunk and extremities. She also developed lichenoid papules with itching on her back. Histologically, both the pigmented and the papular lesions had amyloid deposits beneath the epidermis. In this case it is presumed that the papular lesions with amyloid (lichen amyloidosus) developed initially from friction melanosis which became macular pigmented lesion (macular amyloidosis). The etiologic factor of these sequential pathologic changes is considered to be repeated scrubbing with nylon towels.