Beyond the surface - an uncommon case of Microsporum gypseum subcutaneous mycosis induced by an insect bite

Sep 30, 2026

Deep cutaneous and subcutaneous infections caused by dermatophytes are exceptionally rare and usually require traumatic inoculation. This clinical report describes the diagnostic and therapeutic course of a 24-year-old immunocompetent patient with a subcutaneous mycosis due to Microsporum gypseum after an insect bite–associated lesion. The case highlights initial misdiagnosis as pyoderma gangrenosum, subsequent biopsy and culture reassessment, and the ultimately effective use of terbinafine, achieving complete remission. The report emphasizes recognizing rare epidermomycosis when history and morphology fit the hypothesis.

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CategoryHealthcare

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Abstract

Introduction

Case Report

Dermatology Reports 2025; volume 17:10266 Beyond the surface: an uncommon case of Microsporum gypseum subcutaneous mycosis induced by an insect bite Mariateresa Rossi, Benedetta Galli, Grazia Linda Artelli, Laura Grigolato, Piergiacomo Calzavara-Pinton Dermatology Department, University of Brescia, Italy Abstract Deep cutaneous and subcutaneous infections caused by dermatophytes are exceptionally uncommon, typically occurring through traumatic inoculation. This clinical report details the complex dermatological journey of a young, immunocompetent 24-year-old girl who reported a rare case of a subcutaneous mycosis caused by Microsporum gypseum. The patient presented with an annular erythematous plaque with centered papules on her lefthand, which she referred to as stemming from an insect bite. Initial evaluation at another hospital included a biopsy, which resulted ina preliminary diagnosis of pyoderma gangrenosum. Appropriate treatment with topical steroids and later oral cyclosporine provid- Correspondence: Laura Grigolato, Dermatology Department, University of Brescia, Piazzale Spedali Civili 1, 25121 Brescia, Italy. E-mail: [l.grigolato001@studenti.unibs.it](l.grigolato001@studenti.unibs.it) Key words: dermatophytes; subcutaneous mycosis; Microsporum gypseum. Conflict of interest: the authors declare no potential conflict of interest. Ethics approval and consent to participate: no ethical committee approval was required for this case report by the Department because this article does not contain any studies with human participants or animals. Informed consent was obtained from the patient included in this study. Consent for publication: the patient gave her written consent to use her personal data for the publication of this case report and any accompanying images. Availability of data and materials: all data underlying the findings are fully available. Received: 22 January 2025. Accepted: 11 April 2025. This work is licensed under a Creative Commons AttributionNonCommercial 4.0 International License (CC BY-NC 4.0) . ©Copyright: the Author(s), 2025 Licensee PAGEPress, Italy Dermatology Reports 2025; 17:10266 doi:10.4081/dr.2025.10266 Publisher's note: all claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and thereviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher. ed no response, leading clinicians to perform a new biopsy and cultural examination; the patient was diagnosed with epidermomycosis and pustular folliculitis caused by M. gypseum, ageophilic dermatophyte. In our patient’s case, terbinafine proved effective, resulting in complete remission. This article aims to emphasize the importance of considering rare conditions such as subcutaneous epidermomycosis when the patient’s medical history provides suggestive clues, particularly if the clinical manifestation aligns with the hypothesis. Introduction Epidermomycosis refers to a fungal skin infection caused by dermatophytes, a group of fungi that commonly infect the skin, hair, and nails. Microsporum gypseum, a wild geophilic dermatophyte that primarily derives its infection source from the environment, can infect humans and various animals, predominantly resulting in skin diseases.1 While infrequently responsible for human infections, this fungus has been implicated in skin and hair infections, particularly in tinea barbae. Research on dermatophytoses across various global regions indicates that M. gypseum infections are uncommon compared to those caused by Trichophyton rubrum, Trichophyton mentagrophytes, and Microsporum canis.2-4 Dermatophytes typically target the keratinized layer of skin, hair, and nails, with their growth confined to the outermost dead zones. Nonetheless, in cases of mechanical skin b

FAQs

Why are dermatophyte-related deep cutaneous and subcutaneous infections uncommon?

They are exceptionally rare because they typically require traumatic inoculation for fungi to penetrate beyond the usual superficial keratinized layers.

What caused the initial misdiagnosis in this case?

The patient’s lesion was initially evaluated at another hospital and the biopsy led to a preliminary diagnosis of pyoderma gangrenosum.

Which treatment proved effective and what was the outcome?

Terbinafine proved effective in this patient, resulting in complete remission.

Sep 30, 2026

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