Diagnostic challenges and the evolving landscape of tinea infections

In their manuscript entitled “Eruptive inflammatory tinea corporis: a case report highlighting the role of molecular testing on formalin-fixed tissue in confirming the causative species”, Goode et al. describe a young woman who developed a slowly expanding, blistering, papulovesicular, and crusted eruption that mimicked inflammatory dermatoses and initially obscured the diagnosis of tinea corporis (1). Histopathology demonstrated septate hyphae and broad-range polymerase chain reaction performed on formalin-fixed biopsy tissue identified Microsporum canis, a zoophilic dermatophyte, with household exposure traced to a pet dog. The patient’s fiancé had a similar clinical presentation and both patients and the dog cleared with treatment without recurrence at 6 months. This case exemplifies several key challenges in the contemporary diagnosis and management of dermatophyte infections, including marked clinical variability, limited access to confirmatory testing, and the need for judicious antifungal use.

Reliance on visual diagnosis alone for suspected dermatophytosis, a common practice in primary care settings, can lead to diagnostic errors and delays in appropriate therapy (2,3). Although formal data evaluating the accuracy of visual diagnosis for tinea infections are limited, prior work has demonstrated high rates of diagnostic discordance in primary care management of cutaneous disease; in a single-center prospective survey of 260 patients seen in dermatology practice in whom prior primary care diagnostic or treatment errors were identified, 88% of the 319 documented errors involved misdiagnosis. In that study, dermatophyte infections accounted for 102 diagnostic errors (32% of all errors) and comprised 29% of all erroneously made diagnoses, making it the most frequently misdiagnosed condition (4). In a 2016 survey of board-certified dermatologists asked to determine whether 13 clinical images represented fungal infection, accurate categorization exceeded 75% in only 4 cases (5). Although classic annular plaques are the most commonly described presentation of dermatophytosis, infections caused by zoophilic dermatophyte species can provoke a markedly inflammatory response (6-8). These presentations may be atypical and can include vesiculobullous or crusted lesions with intense erythema and scale, sometimes mimicking eczematous dermatitis, bullous dermatoses, or autoimmune blistering disorders (9,10). Atypical dermatophyte infection presentations can create diagnostic challenges and delay appropriate treatment, as illustrated in the accompanying case report (1). Conversely, empiric antifungal therapy without confirmation may delay diagnosis, exacerbate symptoms, expose patients to unnecessary medication risks, and contribute to antifungal selection pressure (11). Although this was not an issue in the case report, misdiagnosis can be further compounded by the widespread empiric use of topical corticosteroids, which can modify lesion morphology and produce steroid-altered (“tinea incognito”) presentations (12). As dermatophyte epidemiology continues to evolve, with emerging species and shifting transmission patterns, reliance on morphology alone might become increasingly unreliable.

Despite longstanding recognition of limitations to visual diagnosis, access to and use of mycologic testing remain inconsistent across clinical settings (2,3,13-15). Many outpatient healthcare settings lack basic microscopy infrastructure and training (3,16). Fungal culture and polymerase chain reaction testing are often unavailable, associated with prolonged turnaround times, or limited by cost, low reimbursement, and Clinical Laboratory Improvement Amendments (CLIA) certification requirements and operational burden (17-19). These structural barriers, combined with training gaps and workflow constraints, perpetuate a cycle in which empiric treatment substitutes for confirmatory diagnosis, even when confirmatory testing might meaningfully alter management (11,20).

Beyond mycologic testing, the diagnostic value of a thorough clinical and exposure history may be underappreciated. Animal contact, particularly with household pets, remains a key risk factor for zoophilic dermatophyte infections, as highlighted by Goode et al. (1). Similarly, concurrent or recent rashes in household members or close contacts may suggest transmissible fungal disease rather than inflammatory dermatoses (1). Emerging reports of sexually associated transmission of dermatophyte infections, particularly those involving Trichophyton mentagrophytes genotype VII (TMVII), further underscore the importance of incorporating targeted exposure questions into routine dermatologic evaluation (21,22).

Fortunately, the infection in this case responded to standard antifungal therapy. However, it occurred within a rapidly changing global tinea infection landscape. Historically regarded as benign and easily treated, dermatophyte infections have increasingly emerged as a public health concern because of antifungal drug resistance (2,23,24). Over the past decade, emerging dermatophyte species and subspecies have driven outbreaks of extensive, highly pruritic, and treatment-refractory infections. Most notably, Trichophyton indotineae has emerged as a cause of widespread, multi-site tinea requiring prolonged courses of systemic antifungals (25-27). Many infections fail to respond to standard-dose oral terbinafine and instead require itraconazole, which presents additional challenges related to tolerability, drug-drug interactions, and monitoring (25). In an era of emerging terbinafine resistance, species-level identification may increasingly guide therapeutic selection (11,28).

The shifting landscape of dermatophyte infections underscores the need for improved recognition, expanded access to diagnostic testing, and more judicious antifungal use (11). The case presented by Goode et al. serves as a timely reminder that dermatophyte infections can no longer be considered uniformly simple or benign. Improving recognition and diagnostic precision will likely require expanded access to point-of-care microscopy and molecular testing, integration of laboratory confirmation into routine workflows when feasible, and greater incorporation of exposure history into clinical assessment (7,29). Efforts to strengthen diagnostic infrastructure and antifungal stewardship across outpatient settings may help preserve therapeutic options as dermatophyte epidemiology continues to evolve.

Acknowledgments

ChatGPT (OpenAI) was used for language editing of this manuscript; all intellectual content is the sole responsibility of the authors.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, AME Case Reports. The article did not undergo external peer review.

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://acr.amegroups.com/article/view/10.21037/acr-2026-0064/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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