Collecting Puzzle Pieces

A 64-year-old man presented to the allergy and immunology clinic for evaluation of an urticarial rash. During the preceding 7 years, he had had outbreaks of a nonpruritic and painless rash approximately once a month. The rash had primarily affected his torso and thighs and spread sporadically to other areas of his body, sparing the face and hands. Each outbreak had lasted for 5 to 7 days, after which it cleared completely, with no residual discoloration. Although the patient did not have skin lesions at the time of presentation, he provided smartphone-based photographs showing previous occurrences in which a classic urticarial pattern was featured (Fig. 1A and 1B).