Bullous reactions to bedbug bites reflect cutaneous vasculitis

Background: There has been a worldwide resurgence of bedbug infestations. Bites by these insects may cause mild or severe cutaneous reactions, and anaphylaxis has been reported. Little is known about the most severe cutaneous reactions, termed bullous or complex reactions.

Objective: To study the time course and histopathologic findings of complex (bullous) cutaneous reactions to bedbugs in order to determine the optional treatment for them.

Design, setting, and participants: We prospectively photographed bullous reactions to observed bedbug bites at 30 minutes; 6, 12, 24, 36, 48, and 72 hours; 1, 2, 3, and 4 weeks, and biopsied reactions at 30 minutes, and 6, 12, and 24 hours. We also reviewed Internet postings and the available medical literature on bullous reactions after bedbug bites.

Main outcomes and measures: Correlations between clinical and histologic findings using both routine and immunofluorescent techniques.

Results: Bullous reactions to bedbugs are not rare. Of 357 photographs of bedbug bites posted on the Internet, 6% were bullous. In an individual with previous bullous reactions, experimental bedbug bites were associated with a progression of cutaneous responses at bite sites from immediate, pruritic, edematous lesions to a late-in-time macule, which evolved into bullous reactions by 24 hours. Bullous lesions eventually lysed but took weeks to heal. Histopathologic evaluation of bullous reactions showed a polymorphous picture with histologic evidence of an urticarial-like reaction early on that rapidly developed into a hybrid leukocytoclastic vasculitis. This vasculitis was initially neutrophilic but developed into a destructive, necrotizing, eosinophil-rich vasculitis with prominent infiltration of CD 68+ histiocytes and collagen necrobiosis. This histologic picture is similar to the dermal vasculitis in patients with Churg-Strauss vasculitis.

Conclusion: Historically, bedbug bite reactions have been considered to be of minor medical significance. However, the findings presented here demonstrate that the not-uncommon bullous reactions to bedbug bites reflect the presence of a local, highly destructive, cutaneous vasculitis. The histologic features of these reactions resemble those occurring in the Churg-Strauss syndrome. Therefore, efforts to prevent further bites and monitor for evidence of systemic vasculitis should be made in patients with bullous reactions to bedbug bites. Topical treatment with high potency corticosteroids may be useful in the treatment of bullous reactions.