P320 Ten cases of tinea incognito due to Trichophyton rubrum, and literature review on the pathogenic characteristics
Authors: Zhou Xin , Sybren De Hoog , Feng Peiying 
Published: September 2022

Abstract

Poster session 2, September 22, 2022, 12:30 PM - 1:30 PM

Objective
We present ten tinea incognito (TI) patients caused by Trichophyton rubrum combined with a review of the characteristics of tinea incognito infections reported worldwide over the past 20 years, leading to clinical requirements for diagnosis and treatment.

Patients and Methods
Patients were scraped for direct KOH microscopy of the skin lesions at the initial visit, isolates were cultured in SDA medium for 14 days and species were identified by morphology and molecular analysis using ITS regions. Literature review by searching articles on ‘PubMed’ and ‘Web of Science’, using the keywords ‘Tinea incognito or Incognito’, Set the year as ‘2002-2022’, and screened the literature for cases with clear types of TI infecting pathogens. Clinical, mycological, and treatment data of all cases were collected and analyzed.

Results
We report 10 cases of tinea incognito caused by T. rubrum, ranging in age from 5 to 70 years, with clinical manifestations of eczema-like (Figs. 1a, b, and f), SLE-like (Fig. 1d) and pustular psoriasis-like (Figure 1c, e, g, h, i and j), seen in multiple sites. All of our patients had either tinea pedis or onychomycosis themselves or in their family members.
A total of 660 cases reported in the last 20 years, T. rubrum (279/660) was the main anthropophilic dermatophytes causing TI, T. mentagrophytes (162/660) and Microsporum canis (135/660) were the common zoophilic pathgens. There were median age differences in patients infected with T. rubrum, T. mentagrophytes, M. canis, and Nannizzia gypsea, at 56, 22.5, 23, and 5.5 years old, respectively (Fig. 2a). The TI patients infected by T. rubrum often had cutaneous or non-cutaneous underlying diseases (27/41), TI patients with zoophilic or geophilic dermatophyte infections had a definite animal or soil contact history (114/136). The face and trunk are the most frequently affected areas, followed by the extremities and the whole body (Fig. 2b). TI appears on the face and is often thought of as eczema, rosacea, DLE, photosensitive rash, and when it occurs on the trunk is misdiagnosed as eczema, pyoderma, psoriasis (Fig. 2c). In Asia and the Americas, anthropophilic dermatophytes are by far the most reported pathogens, especially T. rubrum. In Europe, zoonotic pathogens have been reported in excess of the anthropophilic (Fig. 2d). For patients in whom the nature of the lesions cannot be determined and with negative direct microscopic examination, dermoscopy can be used to aid in the diagnosis. Our review of all cases found that topical or systemic antifungal treatment always gave good efficacy.

Conclusion
TI has a broad spectrum of mimics, and an unrestricted range of target audiences, zoonotic pathogens are adapting to the human host, so the history of illness and contact is essential at the time of the initial visit. A definitive diagnosis must be obtained in a mycological laboratory, multiple modalities can be used to diagnose TI, and systemic antifungal treatment is often necessary.