Merkel cells and prurigo nodularis.

BACKGROUND: Increased numbers of dermal nerves have been demonstrated in prurigo nodularis and have been theoretically linked to the intense pruritus. We hypothesized that the neuronal proliferation in prurigo nodularis might be associated with an increased density of Merkel cells because they are also a component of the neurocutaneous system.

METHODS: We examined skin biopsy specimens from 20 cases of prurigo nodularis for Merkel cells with the use of a standard immunohistochemical assay (avidin-biotin-peroxidase complex system) with an antibody to cytokeratin 8 (CAM 5.2). Six cases of lichen simplex chronicus were examined as controls.

RESULTS: Merkel cells were present in the interfollicular area of the basal cell layer in 15 (75%) of 20 prurigo nodularis cases and in one (17%) of six cases of lichen simplex chronicus.

CONCLUSION: Merkel cells are increased in number in prurigo nodularis and may be a component of the neurocutaneous abnormality associated with this disorder.