Bullous Insect Bite Reaction with Flame Figures

A 25-year-old male with no known comorbidities presented with complaints of multiple, itchy fluid-filled lesions over feet of 2 days duration. The patient provided a history of being bitten by insects while walking barefoot in the field, following which he developed immediate itching and burning sensations. The next day, he noticed fluid-filled lesions on the site of bites. There was no history of fever. There was no history of similar lesions in the past. Dermatological examination revealed the involvement of dorsum of bilateral feet in the form of multiple, discrete, monomorphic, tense bullae, and largest measuring 2 cm × 1 cm over right great toe [Figure 1a and b]. The complete blood count was normal. Skin biopsy for histopathology revealed a subcorneal split in the epidermis. There was moderate-to-dense mixed inflammatory infiltrates comprised of numerous eosinophils and lymphocytes in the deep dermis and subcutis [Figure 2a]. On higher magnification, the degraded eosinophils were seen to be coating the collagen bundles with major basic protein (MBP) leading to the formation of flame figures [Figure 2b]. On the basis of clinical findings and histopathology, he was diagnosed with a case of insect bite hypersensitivity and was managed with a short course of tablet prednisolone 60 mg once daily for 5 days, following which lesions resolved leaving behind postinflammatory hyperpigmentation.Figure 1: (a and b) Multiple, polysized, discrete vesicles, and bullae over the feet at site of insect biteFigure 2: (a) A sub-corneal split in the epidermis. There is moderate-to-dense inflammatory infiltrate in the deep dermis and subcutis (H and E, ×20), (b) On higher magnification, the inflammatory infiltrate is mixed composed of eosinophils and lymphocytes. Degranulating eosinophils are coating the collagen bundles with major basic protein and leading to formation of flame figures (H and E, ×40)Flame figures as histopathological findings were first described by George Wells in 1971 as focal deposits of amorphous material associated with collagen fibers in the dermis in patients with eosinophilic cellulitis or Wells' syndrome.[1] However, flame figures have also been reported in other eosinophilic dermatoses such as bullous pemphigoid and insect bites reactions.[2] They are foci of intense eosinophilia of the collagen bundle which are believed to occur due to staining of collagen bundles by the MBP secreted by the eosinophils infiltrating the dermis.[2] In general, initial findings of eopsinophilic dermatoses consist of a nonspecific, superficial, and deep lymphocytic and eosinophilic dermal infiltrate.[3] Edema, especially in the papillary dermis, is usually seen. Flame figures develop over 1–3 weeks.[4] Our case was presented 2 weeks after insect bites. For insect bite-induced flame figures, depending on the severity of pruritus, topical/intralesional/systemic steroids are indicated.[5] Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.