Mimicry of Symptomatic Dermographism: A Case Series of Atypical Presentations

From the paper

Abstract

Symptomatic dermographism (SD) is the most common form of chronic inducible urticaria, typically presenting with pruritic, linear wheals that appear within minutes after stroking the skin and resolve within 30 minutes. However, not every linear urticarial eruption following friction or scratching is true SD. We present three clinical cases initially misdiagnosed or suspected as classic SD, but which after detailed evaluation proved to be different entities. The first case was an atypical follicular subtype of SD itself, with a false-negative initial FricTest. The second case was cholinergic dermographism — a rare variant of cholinergic urticaria requiring two concurrent triggers (sweating and stroking) — in a patient with hyperhidrosis. The third case was flagellate dermatitis caused by consumption of inadequately cooked Shiitake mushrooms, with lesions persisting for days and no response to antihistamines. These cases highlight that even a characteristic linear wheal pattern is not pathognomonic for SD. A thorough history, recognition of atypical morphologies, and appropriate provocation testing (including combined triggers when needed) are essential to avoid diagnostic pitfalls and initiate effective therapy.