Demonstration by S-100 protein staining of increased numbers of nerves in the papillary dermis of patients with prurigo nodularis.

Abstract

We hypothesized that hyperplasia of papillary dermal nerves was a constant feature of prurigo nodularis. We tested this hypothesis by examining sections from 25 cases of prurigo nodularis, 25 cases of skin lesions characterized by epidermal hyperplasia without clinical pruritus, and 22 cases of clinically pruritic dermatoses with variable degrees of epidermal response for the presence of papillary dermal nerves. We used a standard immunohistochemical assay with an antibody to S-100 protein as a means of identification of nerves. In 24 of 25 cases of prurigo nodularis, papillary dermal nerves were identified by immunostaining. Cutaneous nerves were present in 1 of 22 cases of epidermal hyperplasia with pruritus and were absent in the papillary dermis in nonpruritic cases. We conclude that hypertrophy of cutaneous papillary dermal nerves is a relatively constant feature of prurigo nodularis. The presence of papillary dermal nerves suggests a neurocutaneous component in the pathogenesis of prurigo nodularis.