In addition to a case of multiple acral fibrokeratomas, 28 cases of solitary, acral, fibrous nodules are reviewed. Evidence from a study of less developed lesions from the patient with multiple acral fibrokeratomas suggests that fibrokeratomas are the result of an overgrowth of the papillary dermis. The early lesions are indistinguishable from those seen in prurigo nodularis. The 28 solitary, fibrous nodules were divided histologically into acral fibrokeratomas (15 cases), irritation fibromas (five cases), and fibromas molle (eight cases). Acral fibrokeratomas are histologically indistinguishable from the periungual and subungual fibromas seen in the tuberous sclerosis complex. Fibromas molle polyps are the result of an overgrowth of the reticular dermis. Irritation fibromas show a random pattern of hyalinized collagen bundles and are apparently derived from or replace the reticular dermis.
Reed RJ, Elmer LC. Multiple Acral Fibrokeratomas (A Variant of Prurigo Nodularis)Discussion of Classification of Acral Fibrous Nodule and of Histogenesis of Acral Fibrokeratomas. Arch Dermatol. 1971;103(3):286-297. doi:10.1001/archderm.1971.04000150056008