Tinea Incognito

Abstract

A 1-year-old male child had a past medical history of mild atopic dermatitis in the first months of life, successfully treated with intermittent topical steroid therapy. Because of the reappearance of similar lesions in the recent period, he was treated with antibiotics and oral steroids by the general practitioner. Despite such therapy, skin eruption worsened and expanded, and the patient was then referred to our institution. Initial evaluation revealed a child in good general condition with sharply demarcated, scaly erythematous patches on the upper trunk, shoulders, and back (Figure 1); small pustules were also evident. Remaining physical examination was negative. The patient was apyretic. Laboratory tests showed no alterations of white blood cells count, lymphocyte subpopulations, erythrocyte sedimentation rate, and C-reactive protein. Pustular psoriasis was suspected, and topical corticosteroid therapy was undertaken. Despite treatment, skin lesions progressed; a diagnostic skin biopsy was then performed, revealing dermatophytic fungal hyphae of Trichophyton mentagrophytes species. Such findings suggested a primary diagnosis of tinea incognito (TI), worsened by steroid therapy and mimicking pustular psoriasis. Oral fluconazole (6 mg/kg/d) and topical miconazole were then started. After 4 weeks, complete resolution of skin erythema and pustules was observed on trunk and back (Figure 2; available at www.jpeds.com). TI is a dermatophytosis with atypical features because of the absence of classic appearance of cutaneous tinea (ringworm), usually caused by prolonged use of steroids.1Romano C. Asta F. Massai L. Tinea incognito due to Microsporum gypseum in three children.Pediatr Dermatol. 2000; 17: 41-44Crossref PubMed Scopus (47) Google Scholar Mistreatment of tinea infection with topical corticosteroid therapy may lead to a variety of skin presentations, including lichenoid, rosacea-like, eczema-like, and psoriasis-like TI.2Gorani A. Schiera A. Oriani A. Case report. Rosacea-like tinea incognito.Mycoses. 2002; 45: 135-137Crossref PubMed Scopus (38) Google Scholar The mechanism by which dermatophytes lead to pustular lesion development in psoriasis-like TI is poorly understood. It is known that dermatophytes are able to stimulate production of interleukin 8 by human keratinocytes3Tani K. Adachi M. Nakamura Y. Kano R. Makimura K. Hasegawa A. et al.The effect of dermatophytes on cytokine production by human keratinocytes.Arch Dermatol Res. 2007; 299: 381-387Crossref PubMed Scopus (54) Google Scholar which, in turn, induces neutrophil chemotaxis. Local neutrophil activation may contribute to the development of pustules.4Davies R.R. Zaini F. Drugs affecting Trichophyton rubrum-induced neutrophil chemotaxis in vitro.Clin Exp Dermatol. 1988; 13: 228-231Crossref PubMed Scopus (8) Google Scholar Two published cases of TI characterized by pustular inflammatory skin lesions are similar to our patient.5Kawakami Y. Oyama N. Sakai E. Nishiyama K. Suzutani T. Yamamoto T. Childhood tinea incognito caused by Trichophyton mentagrophytes var. interdigitale mimicking pustular psoriasis.Pediatr Dermatol. 2011; 28: 738-739Crossref PubMed Scopus (7) Google Scholar, 6Serarslan G. Pustular psoriasis-like tinea incognito due to Trichophyton rubrum.Mycoses. 2007; 50: 523-524Crossref PubMed Scopus (36) Google Scholar The presentation of pustular psoriasis-like TI may cause potential confusion in the initial diagnosis, which includes juvenile-type pustular psoriasis, subcorneal pustular dermatosis, and impetigo (Figures 3 and 4; available at www.jpeds.com). Skin swab and/or skin punch biopsy are advisable to detect fungal hyphae in all psoriasis-like clinical pictures unresponsive to steroid therapy; correct diagnosis of TI allows, in turn, onset of appropriate antimicotic treatment and skin lesions healing. Figure 3Juvenile-type pustular psoriasis.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 4Diffuse impetigo.View Large Image Figure ViewerDownload Hi-res image Download (PPT)