A 50-year-old man is referred for evaluation of a rash first noted approximately 2 months ago. He states that the rash is itchy and is accentuated by rubbing and applying pressure. Despite a 2-week course of cetirizine, the condition has not improved. The patient is currently prescribed a thiazide diuretic to control his hypertension. Examination reveals multiple, hyperpigmented macules predominately affecting his chest, abdomen, and back.
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Urticaria pigmentosa characteristically presents as multiple hyperpigmented macules of the trunk. Darier sign is positive, which indicates itching and redness after touching a lesion.1 The itching is attributed to mast cell degranulation and increased production of interleukin (IL)-31.2
The condition is a form of mastocytosis, a group of disparate disorders marked by mast cell proliferation. Other variants of mastocytosis include mastocytoma, mast cell leukemia, and systemic disease involving the skin and internal organs. Some cases have been linked to mutations of c-KIT, a proto-oncogene, as well as to elevations of IL-6.3,4
Diagnosis of urticaria pigmentosa is confirmed by skin biopsy. Treatment is aimed at relief of symptoms as most cases resolve spontaneously. Patients should be instructed to avoid alcohol and drugs that can cause histamine release including aspirin, codeine, and opiates. Oral H1-receptor antagonist and H2-receptor antagonist antihistamines may help to decrease itching and flushing. Both ultrapotent topical corticosteroids and omalizumab may induce remission.5,6
Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as an associate professor of medicine at Commonwealth Medical College and a clinical instructor of dermatology at Arcadia University and Kings College.
1. Valent P. Diagnostic evaluation and classification of mastocytosis. Immunol Allergy Clin North Am. 2006;26(3):515-534.
2. Lange M, Gleń J, Zabłotna M, et al. Interleukin-31 polymorphisms and serum IL-31 level in patients with mastocytosis: correlation with clinical presentation and pruritus. Acta Derm Venereol. 2017;97(1):47-53.
3. Shomali W, Gotlib J. The new tool “KIT” in advanced systemic mastocytosis. Hematology Am Soc Hematol Educ Program. 2018;2018(1):127-136.
4. Desai A, Jung MY, Olivera A, et al. IL-6 promotes an increase in human mast cell numbers and reactivity through suppression of suppressor of cytokine signaling 3. J Allergy Clin Immunol. 2016;137(6):1863-1871.e6.
5. Guzzo C, Lavker R, Roberts LJ 2nd, Fox K, Schechter N, Lazarus G. Urticaria pigmentosa. Systemic evaluation and successful treatment with topical steroids. Arch Dermatol. 1991;127(2):191-196.
6. Jendoubi F, Gaudenzio N, Gallini A, Negretto M, Paul C, Bulai Livideanu C. Omalizumab in the treatment of adult patients with mastocytosis: a systematic review. Clin Exp Allergy. 2020;50(6):654-661.