Prurigo nodularis: a review.

Prurigo nodularis is a chronic condition characterized by a papulonodular pruriginous eruption of unknown aetiology. This condition is a difficult disease to treat and causes frustration to both the patient and the treating doctor. A variety of systemic conditions have been reported to be associated with prurigo nodularis. The mechanism by which these disorders may trigger prurigo nodularis is unknown. Nerve growth factor has been implicated in the pathogenesis of prurigo nodularis. Calcitonin gene-related peptide and substance P immunoreactive nerves are markedly increased in prurigo nodularis when compared with normal skin. These neuropeptides may mediate the cutaneous neurogenic inflammation and pruritus in prurigo nodularis. Topical or intralesional glucocorticoids are the treatment of choice. Other topical treatments such as topical vitamin D3, and topical capsaicin have also been reported to be effective. Oral treatments such as cyclosporin and thalidomide have been shown to improve both appearance of the skin and pruritus. We review the clinical features, associations, pathology, pathogenesis and treatment of prurigo nodularis.