The patient is a 56-year-old Hispanic man who presents with a moderately itchy rash affecting his neck and lower cheek. He spent the previous year in the Dominican Republic; despite treatment with various steroid creams, the rash persisted. Examination reveals well-defined erythematous plaques of the affected areas with raised borders and moderate scale.
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The morphology and clinical history suggested tinea incognito, which was confirmed by fungal culture. When a cutaneous fungal infection goes unrecognized and is treated inappropriately with topical or systemic glucocorticoids, the clinical presentation of the pathogen is modified. The obscured tinea infection is given the designation “incognito” as it tends to mimic other dermatologic infections.1 Tinea is a superficial fungal infection caused by dermatophytes which metabolize dead skin keratinous tissue. Typically, these dermatophytes evoke a localized response in the skin, however immunosuppressants such as topical creams will suppress this response and further enhance fungal growth.
On examination, papules, pustules, and epidermal atrophy may be present secondary to chronic glucocorticoid application.2 Misdiagnoses of this condition include psoriasis, atopic dermatitis, lupus erythematosus, impetigo or rosacea.3 A microscopic examination of skin scrapings prepared with KOH is diagnostic when spores or hyphae are seen. Scrapings can be cultured with dermatophyte test medium; if positive, the medium will change color from amber to red in 10-14 days.2 Treatment with antifungal therapy is recommended.
Dr Schleicher is director of the DermDox Center for Dermatology, as well as an associate professor of medicine at the Commonwealth Medical College and a clinical instructor of dermatology at Arcadia University and Kings College. Lauren Ax is a physician assistant student at Kings College in Wilkes Barre, PA.
- Bornali, D., R. S., & Bobita, B. (2017). Clinic-epidemiological study of tinea incognito with microbiological correlation. Indian Journal of Dermatology, Venereology and Leprology, 83(3), 326-331. Doi: 10.4103/iJdvl.IJDVL_287_16
- Wolff, K., Johnson, R. A., & Saavedre, A.P. (2013). Fitzpatrick’s COLOR ATLAS AND SYNOPSIS OF CLINICAL DERMATOLOGY (7th ed.). New York, NY: McGraw-Hill Companies Inc.
- Atzori L, Pau M, Aste N, Aste N. Dermatophyte infections mimicking other skin diseases: a 154-person case survey of tinea atypica in the district of Cagliari (Italy). Int J Dermatol. 2012;51:410-415