By Gary M. White, MD
Prurigo nodularis is a nodular form of lichen simplex chronicus. Both adult men and women are affected. The patient complains of intense itching and/or the inability not to scratch. It is very common for the patient to say, "My skin does not heal". The truth is that their skin would heal normally if they stopped scratching.
The patient develops hyperkeratotic, lichenified papules and nodules at sites of repeated scratching. The extensor surfaces of the extremities are typically affected. Excoriations and erosions are common. Secondary bacterial infection may occur. One key diagnostic feature is that the skin changes do not occur on the areas where the patient cannot scratch, e.g. the middle of the back.
Rarely some cases of bullous pemphigoid (pemphigoid nodularis) are similar, so one can do DIF (which should be negative in PN).
The patient must--first and foremost--stop scratching. Along with that, a potent topical steroid may be applied (e.g. clobetasol, cordran tape). Tell the patient he/she needs to be diligent about not scratching for 3 weeks to break the cycle. If this fails, intralesional injection is quite effective (e.g. Kenalog 5 mg/cc). Topical doxepin may be tried as it can have a strong anti-itch effect. For patients with more widespread disease, UVB phototherapy can lead to dramatic reduction of pruritus and clearing of the skin. An open study of 30 patients with PN showed a 76% response rate with pregabalin (75 mg/day) given for 3 months [J Clin Pharm Ther. 2013;38:16]. Two patients with severe disease were improved with cyclosporin 3 mg/kg/day initially then tapered [JDT 1999;10;237]. The vascular endothelial growth factor (VEGF) antagonist Bevacizumab dramatically improved the itch of one patient leading the authors to suggest that increased angiogenesis and VEGF expression correlates with disease severity [JEADV 2016;30;1357].
Of note, antihistamines are usually ineffective in suppressing the itch.
Serlopitant is being investigated for the treatment of PN.
A chronically picked nodule on the nape.
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