The patient is a 31-year-old Hispanic woman who is referred for evaluation of dark marks on her upper arms and back. The duration is several months, and she initially denied itching or traumatizing the sites. Medical history is negative for systemic disease. She is not taking any prescriptive medications but does use supplements. Examination reveals multiple hyperpigmented nodules of the affected sites.
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Prurigo nodularis is a chronic disorder of the skin of unknown etiology. The itch-scratch cycle is involved, but it is uncertain if the lesions precede the itching or if the itching causes the lesions.1 Individual lesions demonstrate increased levels of nerve growth factor.2 Patients present with firm nodules that range in color from pink to brown. The lesions are found on the extensor surfaces, usually sparing areas that patients are unable to reach.3
Prurigo nodularis occurs mainly in older adults, with men and women affected equally. The diagnosis is made clinically. Patients often have a history of chronic pruritus, although denial of self-traumatization is common. The main focus of treatment should be on interrupting the itch-scratch cycle.4 Sedating antihistamines may be useful at bedtime to decrease nocturnal itching. Topical steroids, gabapentin, naloxone, and ultraviolet light have proven useful in select cases.5
Rebecca Geiger, PA-C, is a physician assistant on staff at the DermDox Dermatology Center in Hazleton, Pennsylvania. Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College in Scranton, Pennsylvania, and an adjunct assistant professor of dermatology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia.
- Prak AH. Prurigo nodularis. Available at: https://emedicine.medscape.com/article/1088032-overview. Updated on June 5, 2017. Accessed on March 16, 2018.
- Akiyama T, Carstens MI, Carstens E. Enhanced scratching evoked by PAR-2 agonist and 5-HT but not histamine in a mouse model of chronic dry skin itch. Pain. 2010;151:378-383.
- Vaidya DC, Schwartz RA. Prurigo nodularis: a benign dermatosis derived from a persistent pruritis. Acta Dermatovenerol Croat. 2008;16:38-44.
- Mullins TB, Bhimji SS. Prurigo nodularis. StatPearls [Internet]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK459204/. Updated on October 6, 2017. Accessed on March 16, 2018.
- Zeidler C, Tsianakas A, Pereira M, Ständer H, Yosipovitch G, Ständer S. Chronic prurigo of nodular type: a review. Acta Derm Venereol. 2018;98:173-179.