Report Dermatophyte infections mimicking other skin diseases: a 154-person case survey of tinea atypica in the district of Cagliari (Italy) Laura Atzori, MD, Monica Pau, MD, Natalia Aste, MD, and Nicola Aste, MD From the Dermatology Department, Cagliari University, Italy Correspondence Dr. Laura Atzori, MD Clinica Dermatologica Via Ospedale 54 Cagliari 09124 Italy E-mail: laura.atzori@libero.it Conflicts of interest: none. Funds: none. Abstract Background Although usually simple, the diagnosis of dermatophyte infection is sometimes neglected. An observational study has been realized to evaluate the role of corticosteroid exposure (tinea incognito) and of other primary characteristics of the dermatophytosis that from onset mimic other diseases and mislead an unexperienced physician. Materials and methods Between 1990 and 2009, all cases of atypical dermatophytosis mimicking other skin diseases were collected from the more general number of dermato- phyte infections diagnosed at the Dermatology Department of Cagliari University, Italy. Results One-hundred and fifty-four cases (71 male/83 female, 2–81 years old) were studied, with a median of 7 cases/year. The most observed clinical forms were those mimicking impetigo, eczematous dermatitis, lupus erythematosus, polymorphous light eruption, psoriasis, and rosacea. The identified dermatophytes were: Microsporum canis (70 cases), Trichophyton rubrum (43 cases), Trichophyton mentagrophytes var. mentagrophytes (29 cases), Trichophyton mentagrophytes var. interdigitale (six cases), Microsporum gypseum (three cases), Epidermophyton floccosum (two cases), and Trichophyton verrucosum (one case). Diagnostic difficulties are discussed, with special attention to the origin of the pathomorphosis. Conclusions In our experience, clinical atypia is not a mere consequence of corticosteroid therapy but present at the very onset of the illness, due to the variable dermatophyte invasive capacity, the site of invasion, physiological individual, and/or acquired condition, such as excessive washing or sun exposure. Therefore, we suggest using the term ‘‘tinea atypica’’ rather than ‘‘tinea incognito’’ to include all forms of dermatophytosis that do not present the classic features for both primary and secondary pathomorphosis. Introduction Available literature includes many recent studies on derma- tophyte infections that mimic other skin diseases, 1–10 including: rosacea, psoriasiform eruptions, seborrheic der- matitis, lupus erythematosus, atopic dermatitis, contact dermatitis, bacterial infection, and herpes infections. Vari- ation in clinical presentation depends on different condi- tions: first of all fungal invasion ability, which can be favored or contrasted by physiological variation of the host skin barrier, conditioned by the age of the patient, 6 obesity, and immune suppression. The anatomical characteristics of the affected area are also important, because the pres- ence of skin folds and sebaceous glands as well as variable thickness of the corny layer might bar and impede the typi- cal centripetal progression of the ringworm, and favor crusting, inflammation instead of central clearing, vellus hair follicle involvement, or on the contrary cause a heavy dry hyperkeratotic variety. These conditions are frequently evoked in tinea faciei and manuum presentation. 1–4 Acquired conditions, such as tight-fitting clothes in syn- thetic materials, excessive washing, wet warm climate, and/ or sun exposure are other factors able to alter the clinical expression of the dermatophyte infection. Besides, the vast majority of case reports concentrate on the role of inade- quate topical therapy, mainly corticosteroids. 11–15 Ive and Marks 16 in 1968 introduced the term ‘‘tinea incognito’’ to indicate those dermatophytoses characterized by modifica- tions of the clinical picture following the use of topical steroids prescribed as a result of diagnostic error. Systemic steroids used in the treatment of general pathologies can also induce a pathomorphosis of the clinical presentation. 11 410 International Journal of Dermatology 2012, 51, 410–415 ª 2012 The International Society of Dermatology