The condition described herein was first noted by Muto et al. (1977). Since Tanigaki et al. (1983), the causative significance of repeated friction has been recognized. Hidano (1983) coined the term, friction melanosis. The darkening of the skin along the eminent bones, ribs for instance, is common to 69 cases hitherto reported and 5 cases here described. On histological examination, the melanophages situated around subpapillary vessels and in papillary layer is characteristic. Small deposits of amyloid occur, in certain cases, determined by staining with Dylon, after Yanagihara (1981). The presence or absence of amyloid does not interfere with the diagnosis. Along with the clinical and histological features, the presence of history of repeated friction usually with nylon towel and other nylon articles is also necessary for the diagnosis. The friction is the essential cause, though the existence of other precipitating agents is not excluded. Further investigation is needed for estimating whether contact mechanism and solar radiation may be causative or precipitating. The data of various laboratory tests including hormone assays for Addison disease, are in normal range. The most important therapeutic measure is cessation of the friction, which has been proved by Hirone (1983) to be curative.
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