Frictional amyloidosis L99.0; E85.4;

Frictional amyloidosis; reactive amyloidosis; 

Cutaneous amyloidosis caused by constant scratching and rubbing of certain areas of the skin with hard brushes or other objects (nylon brush macular amyloidosis).

Notalgia paraestheticais a clinical example of this form of frictional amyloidosis, which occurs in approximately 10% of cases of this dermatosis. 

Three patients developed focal hyperpigmentation of the skin, which was attributable to prolonged mechanical friction on the skin caused by years of using a rough nylon cloth or a coarse brush. In all cases, amyloid deposits were detected by electron microscopy (Wong CK et al. 1988).

In 1984, Hidano A et al. described 23 cases (19 women and 4 men, ages: 20 and 35 years) with brownish pigmentation (friction melanosis) that appeared over bony structures such as the clavicle, scapula, or vertebrae. The pigmentation typically exhibited a wavy pattern in the upper back and clavicular regions, a zebra-like pattern over the ribs, and stamp-like spots along the spine. Although there were no signs of inflammation, such as itching or scaling, histological examination revealed “post-inflammatory” melanin deposits in the upper dermis. Amyloid was detected in isolated cases.

1. Hidano A et al. (1984) Friction melanosis. Ann Dermatol Venereol 111:1063-1071.
2. Shendrik I et al. (2025) Acral Melanosis with Macromelanosomes (AMM): The First AI-Defined Pathological Entity and Proposal of Provisional Diagnostic Criteria. Cureus 17:e97276.
3. Yoon JH et al. (2021) A Rare Case of Transient Friction Melanosis of the Finger: A Case Report. Ann Dermatol 33:568–571.
4. Venkataram MN et al. (2001) Frictional amyloidosis: a study of 10 cases. Australas J Dermatol 42:176–179.
5. Wong CK et al. (1988) Friction amyloidosis. Int J Dermatol 27:302–307.