A 57-year-old woman with Xeroderma pigmentosum comes for routine follow-up and describes the appearance of a 2 cm whitish and painful nodule on her left leg with a small hole at the top (Fig 1). She has experienced itchiness and a stinging sensation for 2 weeks. The patient did not report any mosquito bites. Dermoscopy evaluation revealed a small hole within the initial hole (Fig 2). The patient had previously received treatment for 7 melanomas and 15 basal cell carcinomas. Considering the high risk of cutaneous metastasis, we requested a dermatologic ultrasound (Fig 3) to aid in the diagnosis. A linear hyperchoic structure with a positive Doppler sign was observed. Occlusion with Vaseline and mechanical expression resulted in the removal of a larva (Fig 4).
Fig 1.
Fig 2.
Fig 3.
Fig 4.
Question 1: Considering the clinical presentation, dermoscopy, and ultrasonographic findings, what is the diagnosis?
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A.
Epidermoid cyst
-
B.
Myiasis
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C.
Furunculosis
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D.
Tungiasis
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E.
Bedbug
Answers:
-
A.
Epidermoid cyst – Incorrect. The epidermoid cysts originate from the follicular infundibulum and contain keratinous fluid. Although it also has a small hole on the top, the punctum, it normally presents with black keratin. The ultrasound image corresponds to an oval-shaped ultrasound structure with a central hypoechoic band.
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B.
Myiasis – Correct. Myiasis corresponds to the invasion of the tissue by dipterous larvae. It occurs worldwide, with a higher prevalence in tropical and subtropical regions. In nontropical areas, it corresponds to the fourth most common travel-associated skin disease. There are 2 types of myiasis: furunculous and cavitary.1,2
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C.
Furunculosis – Incorrect. Normally caused by Staphylococcus aureus, furunculosis presents as a papule or nodule with erythema and pus.
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D.
Tungiasis – Incorrect. Tungiasis appears as a yellow papule with a brown center, normally on the feet. The dermoscopy shows the structures of the flea.3
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E.
Bedbug – Incorrect. Bedbugs are blood-sucking parasites that live on mattresses and sheets worldwide. They are active at night when they bite the skin, resulting in multiple erythematous papules that are itchy.
Question 2: Which agent is responsible for this type of disease?
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A.
Lutzomia longipalpis
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B.
Cochliomyia hominivorax
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C.
Ancylostoma brasiliensis
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D.
Dermatobia hominis
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E.
Madurella mycetomatis
Answers:
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A.
Lutzomia longipalpis – Incorrect. This agent is a mosquito that is responsible for the transmission of Leishmania sp., causing the ulcer of Leishmaniasis.
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B.
Cochliomyia hominivorax – Incorrect. Cochliomyia hominivorax is a fly whose larvae cause cavitary myiasis. It affects tumors, wounds, and necrotic areas with poor hygiene.
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C.
Ancylostoma brasiliensis – Incorrect. Ancylostoma brasiliensis causes cutaneous larva migrans, a filariform larva disease caused by contact with contaminated soil by dog and cat feces. It is the most common skin disease reported by travelers returning from tropical regions.
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D.
Dermatobia hominis – Correct. Dermatobia hominis is distributed mainly in Central and South America, and it is more common in rural areas. This butterfly has red eyes, a yellow face, and a metallic blue and orange midsection. Infestation occurs in humans, cattle, and other mammals. The female bumblebee puts its eggs in a mosquito, fly, or tick, and this agent transmits the egg to the mammal, which grows in the skin.4,5
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E.
Madurella mycetomatis – Incorrect. Madurella mycetomatis and other agents like Nigrograna mackinnonii and Trematosphaeria grisea cause Eumicetoma, a chronic fungus infection that forms tumors and fistulae and eliminates small granules in the lower limbs.
Question 3: What is the necessary treatment for these cases?
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A.
Occlusion + extraction
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B.
Ivermectin
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C.
Albendazole
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D.
Surgery
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E.
Extraction
Answers:
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A.
Occlusion + extraction – Correct. Apply petrolatum, nail polish, bee wax, or anything that should kill the maggot by hypoxia for 3-24 hours, and then mechanical expression is the main successful treatment.
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B.
Ivermectin – Incorrect. Ivermectin is not necessary, as the maggots have hypoxia within a few hours, making it easily extracted. Besides that, it could be used orally before the mechanical extraction.
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C.
Albendazole – Incorrect. Albendazole is an anthelminthic agent used in cutaneous larva migrans and other similar diseases that has no effect on myiasis.
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D.
Surgery – Incorrect. Surgery is too aggressive for infections that can simply be resolved with occlusion and mechanical expression.
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E.
Extraction – Incorrect. As the larvae have a hocked mouth, it is almost impossible to extract them without hypoxia. Forced mechanical extraction facilitates infection and the remaining parts of the larvae inside the body.
Conflicts of interest
None disclosed.
Footnotes
Funding sources: None.
Patient consent: The authors obtained written consent from patients for their photographs and medical information to be published in print and online and with the understanding that this information may be publicly available. Patient consent forms were not provided to the journal but are retained by the authors.
IRB approval status: Not applicable.
Data availability statement: No data are available.
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