Friction amyloidosis.

Three patients developed a peculiar pigmentation arising from prolonged mechanical friction with the skin due to the use of rough nylon towel or back scratcher for many years. Histochemical stains could not show the existence of amyloid in one of the cases, but amyloid deposition was identified in successive electron microscopic investigations in all three cases. Although "friction melanosis" was originally used by others to describe a close relationship between friction and skin pigmentation in a similar disorder, we consider the term "friction amyloidosis" more appropriate for specifying the important role of friction in causing the early stage of macular amyloidosis. Electron microscopic examination is of importance in establishing a firm diagnosis of this disorder.