Knuckle pads (KPs) are benign, asymptomatic, well-circumscribed, freely movable, skin-colored, wartlike, solitary or multiple nodules and plaques up to 40 mm in diameter1 located in the skin overlying the dorsal aspects of the hands and feet. However, any skin site subjected to constant pressure or friction could develop lesions similar to KPs,2 and in such cases, terms such as helodermas, subcutaneous fibromas, tylositas articuli, and discrete keratodermas are more suitable.3,4 No KP differences are found between races, sexes, or age groups. Across all groups, lesions resemble scars, keloids, calluses, clavi, verrucae vulgaris, fibromas, granulomas annulare, gouty tophi, xanthomas, rheumatoid nodules, foreign body reactions, and erythema elevatum diutinum.1,2,5 The diagnosis is clinical. Histopathologic analysis helps to exclude other diagnoses. There are 2 patterns: (1) epidermal, with hyperkeratosis, acanthosis, discrete fibroblast proliferation; and (2) dermal, with marked fibroblast proliferation, thickened collagen fibers, and sometimes hyperkeratosis.3,6-8
Weiss E, Amini S. A Novel Treatment for Knuckle Pads With Intralesional Fluorouracil. Arch Dermatol. 2007;143(11):1447–1462. doi:10.1001/archderm.143.11.1458
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