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An itchy rash over a foot: Dermoscopy clinched the diagnosis

 Department of Dermatology, All India Institute of Medical Sciences, Bhopal, Madhya Pradesh, India

Date of Submission20-Jan-2020
Date of Decision23-Mar-2020
Date of Acceptance17-Apr-2020
Date of Web Publication19-Sep-2020

Correspondence Address:
Suman Patra,
Department of Dermatology, All India Institute of Medical Sciences, Bhopal - 462 020, Madhya Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/idoj.IDOJ_34_20

How to cite this URL:
Gupta P, Asati DP, Patra S. An itchy rash over a foot: Dermoscopy clinched the diagnosis. Indian Dermatol Online J [Epub ahead of print] [cited 2021 Apr 16]. Available from: https://www.idoj.in/preprintarticle.asp?id=295450

A 10-year-old boy presented with an itchy plaque over the right sole for 1 day. The lesion, which was noticed suddenly in the morning, was associated with severe itching and stinging sensation. An irregular shaped brownish plaque 2.5 × 3 cm with a pseudo vesicular appearance at places was noticed over the medial aspect of the right sole on examination [Figure 1]. There was no lesion elsewhere in the body. The initial clinical diagnosis of dyshidrotic eczema was kept. Dermoscopy of the lesion (Heine delta 20T, polarized mode) revealed few structureless, pale-brown areas with numerous dark brown colored tiny thin spines of 0.1 to 0.3 mm length embedded into the keratinous layer [Figure 2]. A possibility of a caterpillar sting was suspected. Further history revealed the presence of many caterpillars in residential area and history of walking barefoot in and around the house by the patient and a caterpillar was detected on the floor of his house [Figure 3]. The patient was counseled regarding the probable diagnosis of caterpillar sting dermatitis and treated with a potent topical steroid to minimize inflammation.
Figure 1: Irregular shaped brownish plaque over the sole with pseudo vesicular lesions at the periphery

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Figure 2: Dermoscopy (10 × magnification polarized mode) showing structureless, pale-brown areas, and numerous tiny dark brown colored spines embedded into the keratinous layer

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Figure 3: The moth caterpillar found at the patient's home

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Caterpillars are larvae form of butterflies and moths. They sometimes cause skin lesions in humans by the “breakaway” spines or hairs that can inadvertently be implanted into the skin.[1] Most reactions in skin are in the form of urticarial wheal, papular urticaria, lesions resembling dermatitis.[2] Rarely the stings and hairs contain venom. Contact with the South American “saturniid” moth or “Lonomia” caterpillars can cause consumptive coagulopathy, intracerebral hemorrhage, and acute renal failure.[3],[4] Lepidopterism refers to a systemic reaction to caterpillars and is characterized by more widespread erythema or urticaria, nausea, vomiting, wheezing, conjunctivitis, headache, etc.[2] The caterpillar species found in India have not been reported to cause severe allergic reactions. In our case, it was probably a moth caterpillar, a common species found in the Indian subcontinent. The color of the spine we noticed on dermatoscopy was similar to that of the caterpillar found in the patient's house. But we could have removed the spines from the foot lesion and examine under a microscope and corroborate with that from the caterpillar found in the house. We also could not perform histopathology from skin lesions due to a lack of parental consent. Our case is unique as it elaborates on an easy identification tool for caterpillar sting induced dermatitis.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

   References Top

Hossler EW. Caterpillars and moths: Part I. Dermatologic manifestations of encounters with Lepidoptera. J Am Acad Dermatol 2010;62:1-10.  Back to cited text no. 1
Hossler EW. Caterpillars and moths: Part II. Dermatologic manifestations of encounters with Lepidoptera. J Am Acad Dermatol 2010;62:13-28.  Back to cited text no. 2
Gamborgi GP, Metcalf EB, Barros EJ. Acute renal failure provoked by toxin from caterpillars of the species Lonomia obliqua. Toxicon 2006;47:68-74.  Back to cited text no. 3
Chan K, Lee A, Onell R, Etches W, Nahirniak S, Bagshaw SM, et al. Caterpillar-induced bleeding syndrome in a returning traveller. CMAJ 2008;179:158-61.  Back to cited text no. 4


  [Figure 1], [Figure 2], [Figure 3]


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