A 38-year-old woman presented with multiple erythematous plaques with scattered pustules predominantly over the malar area and forehead that had been gradually progressing for 8 months. The patient initially noticed slightly scaly, erythematous lesions centered on the midface. There was no reported history of photosensitivity, relevant medications before the eruption, nor a personal or family history of psoriasis.
The lesions initially responded to topical mometasone prescribed for presumed eczema, clearing within 5 days. The patient discontinued the corticosteroid, but the eruption recurred over the next 2 weeks with the development of scattered pustules. Clinical images in the report show the malar and forehead distribution and the pustular component of the eruption (Figure 1A).
Because of the symmetric malar erythema, cutaneous lupus erythematosus was considered. The presence of pustules suggested alternative diagnoses such as pustular psoriasis. Given the atypical morphology and diagnostic uncertainty, a biopsy was performed to guide diagnosis and management.
Topical corticosteroid use has an important role in the evolving appearance of dermatophytosis; suppression of inflammation can produce modified or atypical lesions collectively termed tinea incognito. Over-the-counter fixed-dose creams that include potent corticosteroids are identified as common contributors to this presentation.
A punch biopsy from a lesion on the right cheek was obtained for histologic evaluation. Periodic acid–Schiff (PAS) staining demonstrated spongiosis, subcorneal bullae and fungal hyphae in the stratum corneum. Additional tissue sections stained with Grocott–Gömöri methenamine silver stain highlighted black-coloured fungal hyphae. These findings established the diagnosis of pustular tinea incognito.
The authors note that fungal stains on tissue can reveal hyphae even when clinical appearance mimics other dermatoses, and that biopsy may be required when noninvasive testing has not been performed or is nondiagnostic.
The management approach reported was discontinuation of the topical corticosteroid and initiation of systemic and topical antifungal therapy: oral itraconazole 200 mg and topical luliconazole 1% cream applied twice daily. The patient experienced complete resolution of erythema and pustules within 7 days of therapy (Figure 1B).
The article emphasizes that treatment of tinea incognito involves stopping topical corticosteroids and administering appropriate antifungal agents, both systemic and topical as clinically indicated.
Topical corticosteroid application over dermatophytosis can mask classic fungal features and produce a spectrum of atypical morphologies, creating diagnostic dilemmas. The reported morphologies include bullous, lichenoid, rosacea-like, pustular psoriasis–like and eczema-like presentations. Such variability increases the risk of misdiagnosis and inappropriate corticosteroid prescribing, which may further modify the lesion.
The article highlights over-the-counter fixed-dose creams containing potent corticosteroids as major drivers of tinea incognito. Clinicians should maintain a high index of suspicion for dermatophyte infection in lesions that are atypical in appearance, recurrent after corticosteroid use, or do not fit classical patterns for inflammatory dermatoses.
References cited by the authors address the challenges in diagnosis and management of tinea incognito, atypical presentations of superficial mycoses, and recent updates on dermatophyte epidemiology and treatment.
Consider tinea incognito when erythematous plaques are circular with a raised scaly border, especially if there is a history of topical corticosteroid use or partial steroid response.
Perform skin scraping and potassium hydroxide (KOH) mount to look for fungal hyphae as a rapid, noninvasive diagnostic test.
When the clinical picture is unclear or if noninvasive testing is negative but suspicion remains, obtain a skin biopsy with fungal stains (PAS, Grocott–Gömöri) to detect hyphae and guide treatment.
Management requires cessation of topical corticosteroids and institution of appropriate antifungal therapy; systemic therapy may be indicated depending on extent, location, and prior treatment.
Figure references in the original report illustrate the pre-treatment pustular malar plaques and the post-treatment clearance after 7 days of antifungal therapy. The authors declare no competing interests and obtained patient consent for publication.