The linear trail: A dermoscopic approach to diagnosing cimicosis

A 12-year-old school boy presented to the outpatient clinic with a 3-day history of pruritic, erythematous raised lesions on his hands. Clinical examination revealed multiple erythematous papules with punctate hemorrhagic excoriations arranged in a linear pattern, originating from the first web space and extending toward the forearm bilaterally [Figure 1]. Dermoscopic evaluation demonstrated localized brown-black dots with golden-brownish background suggestive of hemorrhagic bite sites in a linear configuration^[1] [Figure 2]. Based on these findings, a diagnosis of bed bug bite (cimicosis) was established, characterized by the classic “breakfast, lunch, and dinner sign,” indicative of sequential clustered bite marks corresponding to the bug’s movement.^[2] Differential diagnoses, including scabies and paederus dermatitis, were excluded due to the absence of burrows or involvement of other typical sites of predilection, vesicular lesions, and burning sensations.

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Figure 1:

Clinical image of bed bug dermatoses with (a): typical “breakfast, lunch, dinner sign” (black circles) and (b): erythematous pruritic papular eruptions with hemorrhagic puncta in a linear manner (black line).

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Figure 2:

Dermoscopic image of bug bite at web space presenting with (a): brown–black-colored dots (black arrow) and (b): “breakfast, lunch, dinner sign” presenting with similar dots and golden brownish background suggesting hemorrhage at bite sites (black circles and black line). (Illuco IDS 1100, polarised, 10x).

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This case highlights the importance of dermoscopy in distinguishing common insect bite dermatoses such as scabies, cimicosis, and paederus dermatitis, presenting with similar findings. Hemorrhagic spots due to bite marks of bed bugs along with brownish areas due to hemosiderin deposition in a characteristic linear breakfast, lunch, and dinner sign manner provide a useful diagnostic clue to cimicosis.