Wiggling Subcutaneous Lumps

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Diagnosis: Furuncular myiasis due to Dermatobia hominis larvae. Myiasis is the invasion of living tissue by the larvae of several species of flies. In Central and South America, human furuncular myiasis is usually caused by the human botfly, D. hominis [1]. The fertile female fly captures a bloodsucking arthropod (e.g., a mosquito) and attaches eggs to its abdomen and legs. When this egg-carrying mechanical vector lands on a mammalian host, larvae emerge from the eggs and enter the skin of the prospective host. As a larva grows, the site of infestation will show a small, raised, erythematous, furuncular lesion that will evolve into a pruritic and tender nodule that can elicit the sensation of motion (figure 1). The lesion has a central pore that allows the larva to respire from spiracles on its posterior end. It takes 6-12 weeks for the larva to mature fully and to emerge from the skin of its host [2]. The larvae of D. hominis can be removed through the application of lateral pressure, surgical excision, suction with a venom extractor [3], and suffocation with mineral oils [4], petroleum jelly [5], bacon [6], glue, nail polish, or chewing gum. It is difficult to remove the larva because anchoring spines (figure 2B and 2C) counteract the forces used to extract it.