Cutaneous neural proliferation in highly pruritic lesions of chronic prurigo

Abstract

Nodular lesions of chronic prurigo correspond to highly sensitive pruritic areas of neural proliferation. This has been shown by light and electron microscopic studies in four patients. Axons and Schwann cells were participating in this process. Their ultrastructure appeared mostly normal; however, some disorganization, axonal swelling, and dystrophy were also observed. At places, newly formed nervous tissue imitated neuromas, surrounded by mononuclear cells and a peculiar cell type which we called "spider cell." The noninvolved skin near the nodules showed no alterations. Occlusion with elastic bandages for four weeks betters the clinical and histological picture. According to these findings, it seems that the neural proliferation in prurigo is a secondary phenomenon due to chronic traumatization by scratching. We also feel that the extreme pruritus in chronic lesions is related to the increased number of dermal nerves.

Neuronal hyperplasia in the anal canal

“…The location was always in the submucosa, beneath squamous epithelium below the dentate line. For cutaneous nerves it is known that trauma can induce sprouting of nerve fibres (O'Daly & Imaeda 196 7) and it has been suggested that scratching could be of significance in the development of neuronal hyperplasia in prurigo nodularis (Runne & Orfanos 1977). The frequent localization of anal neuronal hyperplasia in haemorrhoids, a mucosal structure exposed to an abnormal irritation and wear, makes it reasonable to suggest that it may arise because of mechanical irritation.…”