A 63-year-old woman is referred for evaluation of an itchy rash affecting both of her legs. The condition was first noted approximately 3 months ago on her left leg and, despite treatment with a variety of home remedies, has not been relieved. She sought medical consultation and was placed on a mid-potency topical steroid that initially relieved the itching; however, the rash persisted. Oral prednisone was commenced with more frequent monitoring of her blood sugar levels, as the patient has diabetes. After 2 weeks on this therapy, the condition worsened, necessitating referral to dermatology.
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Tinea incognito was first defined in 1968 as an aberrant response of an unrecognized cutaneous fungal infection to topical or oral glucocorticoids.1 The clinical appearance of the presenting rash becomes altered, and the involved sites are less scaly and more extensive. Pruritus increases and over time pustules may arise.2
Tinea incognito is frequently misdiagnosed as eczema, impetigo, or psoriasis.3 Regarding the former, tinea incognito has also been reported secondary to the use of the topical calcineurin inhibitors initiated as treatment for presumed eczema.4
Superficial fungal infections are caused by filamentous fungi termed dermatophytes, which are classified into 3 genera: Microsporum, Trichophyton, and Epidermophyton. Diagnosis may be confirmed by fungal culture or by potassium hydroxide (KOH)-enhanced microscopic examination of skin scrapings.4,5
Tinea incognito can be treated either topically or systemically with the method chosen in part by location and severity of the infection.5 Many cases of tinea incognito are extensive and may require oral therapy for full resolution.
Omid Zargari, MD, is a dermatologist at the Skin Research Center in Tehran, Iran. Stephen Schleicher, MD, is director of the DermDox Center for Dermatology in Pennsylvania, as well as an associate professor of medicine at Commonwealth Medical College and a clinical instructor of dermatology at Arcadia University and Kings College.
1. Ive FA, Marks R. Tinea incognito. Br Med J. 1968;3(5611):149-152.
2. Rebell G, Zaias N. Introducing the syndromes of human dermatophytosis. Cutis. 2001;67(5 Suppl):6-17.
3. Romano C, Maritati E, Gianni C. Tinea incognito in Italy: a 15-year survey. Mycoses. 2006;49(5):383-387.
4. Stringer T, Gittler JK, Orlow SJ. Tinea incognito in an urban pediatric population. Cutis. 2018;102(5):370-372.
5. Gupta AK. Tu LQ. Dermatophytes: diagnosis and treatment. J Am Acad Dermatol. 2006;54(6):1050-1055.