The FP suspected that this was a case of dermatographism. To confirm his suspicions, he used the end of a cotton-tipped applicator and wrote on the patient’s skin. Within 3 minutes, the writing turned into a triple reaction with some erythema, blanching, and swelling—confirming the diagnosis.
Dermatographism often accompanies urticaria, but can occur without it. If one writes on the skin, one is able to see the resulting words or shapes. The cause of this condition is unknown, but the pathophysiology involves degranulation of mast cells and the release of histamine.
No treatment is required for asymptomatic dermatographism. If patients are symptomatic, they should be advised to avoid precipitating physical stimuli. Dry skin may stimulate scratching, so the use of emollients can help. If the patient wants a medication, start with a second-generation antihistamine such as loratadine or cetirizine. While the recommended over-the-counter dose of these 2 medications is 10 mg/d, the dose may be increased to 20 mg twice daily. It is best to start at the lowest dose and then titrate up according to response and tolerance of adverse effects. (The second-generation antihistamines can still be sedating.) If this doesn’t work, a sedating antihistamine can be added before bedtime.
Dermatographism is not life-threatening and does not lead to anaphylaxis. The patient in this case didn’t want treatment and was pleased to know what was going on with his skin.
Photos and text for Photo Rounds Friday courtesy of Richard P. Usatine, MD. This case was adapted from: Usatine R. Urticaria and angioedema. In: Usatine R, Smith M, Mayeaux EJ, et al, eds. Color Atlas of Family Medicine. 2nd ed. New York, NY: McGraw-Hill; 2013: 863-870.
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