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A 76-year-old man presents for evaluation of a moderately pruritic rash on his chest that has been present for several weeks. His medical history includes hypertension and hypercholesterolemia but no diabetes or immunosuppression. The patient is a farmer and a dog owner. When the rash first appeared, he was prescribed triamcinolone cream, which he used for 3 weeks and which resulted in gradual worsening of dermatitis. Examination reveals a well-demarcated erythematous patch with raised borders.
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Superficial fungal infections, also known as tinea, are usually caused by filamentous fungi called dermatophytes. Dermatophytes that infect humans belong to 1 of 3 genera: Microsporum, Trichophyton, or Epidermophyton. They may be spread by direct contact from other people (anthropophilic organisms), animals (zoophilic), and soil (geophilic), as well as indirectly from fomites. Tinea incognito is caused by the application of topical glucocorticoids to an unrecognized fungal infection. As a result, the clinical appearance of the initial rash is altered, becoming less scaly, more extensive, pustular, and pruritic.1 The condition may be misdiagnosed as several entities, including impetigo, eczema, psoriasis, and lupus erythematosus.2
Diagnosis of tinea incognito is confirmed by fungal culture or positive potassium hydroxide staining of scrapings. Recently, diagnosis using a handheld confocal microscope has been described.3 Tinea can be treated either topically or systemically. The method chosen depends on the type, severity, and extent of the infection, and on patient preferences.4 The patient described in this case received a 2-week course of terbinafine along with topical econazole cream, which resulted in complete resolution of the rash after 4 weeks.
Kurren Singh Gill is a medical student at the Commonwealth Medical College in Scranton, Pennsylvania. Michael Stas, DPM, is a podiatry-dermatology fellow at St. Luke’s University Hospital in Bethlehem, Pennsylvania, and the DermDox Dermatology Center in Hazleton, Pennsylvania. Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College in Scranton, Pennsylvania, and an adjunct assistant professor of dermatology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. He practices dermatology in Hazleton, Pennsylvania.
References
- Rebell G, Zaias N. Introducing the syndromes of human dermatophytosis. Cutis. 2001;67(5 suppl):6-17.
- Romano C, Maritati E, Gianni C. Tinea incognito in Italy: a 15-year survey. Mycoses. 2006;49(5):383-387.
- Navarrete-Dechent C, Bajaj S, Marghoob AA, Marchetti MA. Rapid diagnosis of tinea incognito using handheld reflectance confocal microscopy: a paradigm shift in dermatology? Mycoses. 2015;58(6):383-386.
- Gupta AK, Tu LQ. Dermatophytes: diagnosis and treatment. J Am Acad Dermatol. 2006;54(6):1050-1055.
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