What is urticaria pigmentosa (cutaneous mastocytosis), and how is it differentiated from common urticaria (hives)?

Updated: Sep 16, 2020
  • Author: Henry K Wong, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Urticaria pigmentosa (cutaneous mastocytosis) is a unique dermatologic disorder caused by infiltration of mast cells in the skin and has a pathology distinct from common urticaria but can present with urticarial lesions associated with blisters. Lesions are hyperpigmented (yellow, tan, or brown) and when lesions are stroked, a linear wheal is formed; this characteristic and diagnostic sign is known as the Darier sign. [31] Although these lesions can become urticarial upon stroking, urticaria pigmentosa is no longer considered a subtype of urticaria, owing to its distinct pathogenetic mechanism involving infiltration by mast cells. [32] Early-onset chronic urticaria is characteristic of autoinflammatory syndromes. [33] Nasal polyposis is associated with aspirin-induced urticaria. [34]

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