A 42-year-old woman presents with a sudden onset of itchy, reddened macules on her trunk. She takes no medications and denies any history of systemic disease. Examination reveals scattered erythematous macules and small wheals located primarily on her trunk. Stroking her skin induces localized erythema and edema.
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Urticaria pigmentosa is the most common cutaneous manifestation of mastocytosis. Mastocytosis represents a group of disparate disorders of mast cell proliferation. Patients present with multiple hyperpigmented to erythematous macules of the trunk and extremities. The rash typically spares the palms and soles.1 Darier’s sign is positive, which refers to swelling, itching, and redness after stroking a lesion.2
Urticaria pigmentosa has a bimodal temporal distribution. The rash typically develops in infancy or early childhood and resolves by puberty. The incidence increases again between ages 30 and 49. Men and women are affected equally, with most cases being reported in Caucasians.3 Unlike the pediatric variant, the majority of adults with this disorder manifest mutations of c-Kit.
Diagnosis is suspected by history and examination and is confirmed by skin biopsy. Patients should be instructed to avoid alcohol, narcotics, and drugs that can cause a histamine response. Treatment is aimed at symptomatic relief. H1 and H2 antihistamines can help to decrease itching and flushing. Ultrapotent topical corticosteroids may induce remission.4
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.
- Quinio M, Torres M. Urticaria pigmentosa in a 6-month old Filipino male with G6PD deficiency. J Am Acad Dermatol. 2016;74(Suppl 1):AB219.
- Vaes M, Benghiat FS, Hermine O. Targeted treatment options in mastocytosis. Front Med. 2017;4:110.
- Worobec AS, Akin C, Scott LM, Metcalfe DD. Cytogenetic abnormalities and their lack of relationship to the Asp816Val c-kit mutation in the pathogenesis of mastocytosis. J Allergy Clin Immunol. 1998;102:523-524.
- Habashy J. Mastocytosis. Medscape. http://emedicine.medscape.com/article/1057932-overview. Accessed October 25, 2017.