Exogenous pigmentation after Diplopoda exposure leading to a dermatoscopic parallel ridge pattern on the plantar region

Abstract

The millipedes (also known as "gongolos") are arthropods characterized by a cylindrical body consisting of rings. When threatened, they release chemicals that can cause erythema and hyperpigmentation. We report the case of a patient who developed a darkened macule on the plantar region after stepping on a millipede. Dermatoscopic examination showed a parallel-ridge pattern, which is considered typical for acral melanoma. A detailed history was essential for the diagnosis, as the clinical and dermatoscopic features suggested a malignant melanocytic lesion.

Four cases of exogenous acral pigmentation related to a darkling beetle (coleoptera: tenebrionidae: blaps)

“…It is important to know that many other species of coleoptera and others insects release a dark hemolymph and can be implicated in such eruption. 1,2,[7][8][9] Interestingly, in all our patients, the morphology and location of the dermatitis were similar. All patients had well demarcated acral pigmented area typically associated with a red or light brown halo.…”

“…On dermoscopy, parallel-ridge pattern is evocative of melanocytic nevi, lentiginosis, early acral melanoma and exogenous pigmentation. [7][8][9] Histological study detected features of exogenous pigment, which made the diagnosis no more doubtful.…”

Occurrence of erythemato-purpuric patches upon contact with a myriapod (diplopod)

“…In this case, the inflammatory response induced epidermal necrosis, which was assessed using erythemato-purpuric staining, followed by desquamation with achromia on the topography of the damage, reactionary erythema, and perifollicular hyperchromia ( Figure 1 ). Such spots usually disappear after a few weeks or months without scarring 3 .…”