The rash morphology and unresponsiveness to instituted therapy, raised the diagnostic hypothesis of Tinea incognita (TI). Skin scrapings were collected and mycological culture was positive to Trichophyton mentagrophytes, confirming the diagnosis. She was treated with oral itraconazole 5 mg/kg/day and topical sertoconazole for 8 weeks, with full recovery.
TI is a dermatophytosis that lacks its classical clinical features due to inadequate use of immunosuppressive therapy, generally corticosteroids (topical or systemic).
1,2 Other agents, such as calcineurin and tumor necrosis factor inhibitors and fumaric acid esters, have also been implicated.
3,4 It represents approximately 40% of all tinea diagnosis.
1
Immunosuppressants inhibit the local cutaneous immune response, allowing fungal infection to spread with an atypical presentation, mimicking various diseases, including eczema (most frequently), contact dermatitis, psoriasis, lupus erythematosus, folliculitis or impetigo.
1,2
Unlike typical tinea, which is characterized by erythematous annular centrifugal lesions, with central pallor and active scaly margins, TI lesions can be poorly defined, less red and scaly, varying from eczematous-like plaques to papular and pustular lesions,
1.3.4 resulting in a diagnostic challenge, in which a high index of suspicion is required.
Diagnosis is most frequently performed by direct microscopy and mycological culture of skin scrapings. Currently, polymerase chain reaction technique may also be used with higher sensitivity and faster results; however, it does not identify the fungi species. Culture remains the gold-standard for diagnosis, particularly when fungi species identification is essential. Its yield can be very low and thus, if dermatophytosis cannot be ruled-out, it should be repeated.
1,3,4 Tricophyton rubrum is the most commonly isolated agent, followed by
Tricophyton mentagrophytes,
1 but any dermatophyte may cause TI.
Treatment includes removing the immunosuppressive agent, symptom control and anti-fungal therapy, either topical, systemic or both, according to the lesion’s extension and duration. Empirical antifungal should cover the most frequent dermatophytes and be adjusted posteriorly to the isolated fungus. Delayed treatment may contribute to spread of infection with invasion of hair follicles and deeper skin layers, resulting in resistant infections, requiring combined topical and oral therapy
1,4 TI should be treated until full resolution.
TI diagnosis should be considered in cutaneous lesions unresponsive to topical treatments, especially immunosuppressants. Accurate diagnosis is critical to prevent spread of infection and ensure appropriate antifungal therapy. Corticosteroids should be avoided in uncertain skin lesions and the patients should be referred to a specialized dermatologic center.
| References : |
- Zacharopoulou A, Tsiogka A, Tsimpidakis A, et al. Tinea Incognito: Challenges in Diagnosis and Management. J Clin Med. 2024; 13(11):3267.
- del Boz J, Crespo V, Rivas-Ruiz F, et al. Tinea incognito in children: 54 cases. Mycoses. 2011; 54(3):254-8.
- Kokandi AA. Tinea Incognito. Clin Cosmet Investig Dermatol. 2024; 17:993-998.
- Ghaderi A, Tamimi P, Firooz A, et al. Updates on Tinea Incognita: Literature review. Curr Med Mycol. 2023; 9(2):52-63.
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