The Diagnosis: Tinea Faciei
Given the morphology of the plaque, a potassium hydroxide preparation was performed and was positive for hyphal elements consistent with dermatophyte infection (Figure).
Hyphal elements noted on potassium hydroxide preparation were consistent with dermatophyte infection.
Tinea faciei is a fungal infection of the face caused by a dermatophyte that invades the stratum corneum.1 It is transmitted through direct contact with an infected individual or fomite.2 Infections typically are characterized by annular or serpiginous erythematous plaques with a scaly appearance and advancing edge. There may be associated vesicles, papules, or pustules with crusting around the advancing border.3 Tinea faciei can occur concomitantly with other dermatophytic infections and frequently presents atypically due to different characteristics of facial anatomy when compared to other tinea infections. As a result, it often is misdiagnosed.1
Tinea faciei represents roughly 19% of all superficial fungal infections and occurs more commonly in temperate humid regions.4 It can occur at any age but has bimodal peaks in incidence during childhood and early adulthood.5 The most common causative dermatophytes are Trichophyton tonsurans, Microsporum canis, Trichophyton mentagrophytes, and Trichophyton rubrum.1 Transmission is mainly through direct contact with infected individuals, animals, or soil, which likely occurred during the close quarters and exercises our patient experienced during basic training in the military.
Tinea faciei often is misdiagnosed and treated with topical corticosteroids. The steroids can give a false impression that the rash is resolving by initially decreasing the inflammatory component and reducing scale, which is referred to as tinea incognito. Once the steroid is stopped, however, the fungal infection often returns worse than the original presentation. The differential diagnosis includes subacute cutaneous lupus erythematosus, periorificial dermatitis, seborrheic dermatitis, psoriasis, rosacea, erythema annulare centrifugum, granuloma annulare, sarcoidosis, and contact dermatitis.1,3,6
Diagnosis of tinea faciei is best made with skin scraping of the active border of the lesion. The scraping is treated with potassium hydroxide 10%. Visualizing branching or curving hyphae confirms the diagnosis. Fungal speciation often is not performed due to the long time needed to culture. Wood lamp may fluoresce blue-green if tinea faciei is caused by Microsporum species; however, diagnosis in this manner is limited because other common species do not fluoresce.7
Options for treatment of tinea faciei include topical antifungals for 2 to 6 weeks for localized disease or oral antifungals for more extensive or unresponsive infections for 1 to 8 weeks depending on the agent that is used. If fungal folliculitis is present, oral medication should be given.1 Our patient was treated with oral terbinafine 250 mg once daily for 4 weeks with follow-up after that time to ensure resolution.