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835 SHORT COMMUNICATION Interdigital Hyalohyphomycosis Caused by Members of the Fusarium solani Species Complex Hiromitsu NOGUCHI 1,2 , Tadahiko MATSUMOTO 1,2 , Masataro HIRUMA 2 , Utako KIMURA 2,3 , Takashi YAGUCHI 4 , Miki HIROSE 6 , Satoshi FUKUSHIMA 6 and Hironobu IHN 6 Noguchi Dermatology Clinic, 1834-1 Namazu, Kashima-machi, Kamimashiki-gun, Kumamoto 861-3101, 2 Ochanomizu Institute for Medical Mycology and Allergology, Tokyo, 3 Department of Dermatology, Juntendo University Urayasu Hospital, 4 Division of Bio-resources, Medical Mycology Research Center, Chiba University, Chiba, and 5 Department of Dermatology and Plastic Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan. E-mail: [email protected] 1 CASE REPORTS The term “Intertrigo” refers simple intertrigo, bacterial in­ tertrigo, candidal intertrigo, interdigital tinea pedis, and in­ tertrigo complicated with erythrasma (1). Interdigital fungal intertrigo is most caused by dermatophytes. In Senegal, Fusarium species are the second most frequently isolated fungi after Candida albicans (2). Human-pathogenic mem­ bers of the genus Fusarium primarily belong to 8 species complexes, of which the Fusarium solani species complex (FSSC) and F. oxysporum species complex account for 60% and 20% (3). Hyalohyphomycosis and phaeohyphomycosis were umbrella terms to cover a growing number of opportu­ nistic mycoses caused by moulds and yeasts whose septate mycelial tissue forms were either hyaline (Gr.’huálinos’), or phaeoid (Gr. ‘phaios’), respectively (4). Here, we provide the first report of interdigital hyalohyphomycosis caused by a member of the FSSC in Japan. Accepted Apr 29, 2019; E-published Apr 29, 2019 Case 1. A 58-year-old, female homemaker with a > 2-year history of an interdigital lesion visited our clinic in February 2017. She presented with maceration, erosion, scales, and itching in the left 3 rd interdigital area (Fig. 1a). Direct microscopy revealed irregu­ larly distorted septate hyphae (diameter 3–8 µm) and intercalary and terminal chlamydoconidia (Fig. 1b). Neither Candida species nor dermatophytes were isolated. Periodic acid-Schiff (PAS)- stained tissue showed septate hyphae. Hematoxylin and eosin (H&E) staining revealed basophilic hyphae (Fig. 1c). Plate culture on Sabouraud’s dextrose agar yielded a white felt-like colony with pale-yellow colored reverse after 7-day incubation at 25°C (Fig. 1d). Slide culture on potato dextrose agar yielded abundant unicellular oval microconidia and septate crescent macroconidia from verticillate conidiophores after 4-day incubation at 25°C. The internal transcribed spacer 1 (ITS-1) region of the rRNA gene and the translation elongation factor 1 alpha (EF-1α) gene sequences showed 100% (206/206 bp) and 100% (702/702 bp) homologies, with Fusarium petroliphilum type strain NF 4475 (NRRL 22268 = FRC S-2176) (5) (Mycobank no. MB802539). Based on its morphological characteristics and the gene analysis results, we identified the isolate as F. petroliphilum (Q.T. Chen & X.H. Fu) Geiser, O’Donnell, D.P.G. Short & N. Zhang, which belongs to the FSSC. The patient was diagnosed with interdigital hyalohyphomy­ cosis. Antifungal susceptibility testing was performed according to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 protocol (6). The minimum inhibitory concentrations (MICs) for the isolate were: amorolfine, 2 μg/ml; amphotericin B, 2 μg/ml; efinaconazole, 2 μg/ml; itraconazole, > 16 μg/ml; ketoconazole, > 16 μg/ml; terbinafine, > 16 μg/ml; and voriconazole, 8 μg/ml. Routine test results were within the normal ranges. The patient was treated with 2% ketoconazole cream and her symptoms disap­ peared in 4 months. The follow-up culture was negative and she showed no recurrence, as of December 2018. Case 2. An 81-year-old, male farmer had noticed an interdigital lesion in 2014. He applied 1% lanoconazole cream, which had no effect. In March 2017, maceration and desquamation in the 3 rd and 4 th interdigital lesions were observed (Fig. 1e). Direct microscopy revealed septate hyphae and chlamydoconidia (Fig. 1f). PAS and H&E-stained tissue also showed septate hyphae (Fig. 1g). Plate culture on Sabouraud’s dextrose agar yielded a white floccose co­ Fig. 1 (a) Case 1: Maceration, erosion, and scales on the left 3 rd interdigital area. (b) Septate hyphae and intercalary chlamydoconidia (potassium hydroxide (KOH) with Parker ink, original magnification ×400). (c) Basophilic septate hyphae (hematoxylin and eosin stain, ×400). (d) Plate culture of Fusarium petroliphilum, a white felt-like colony with pale-yellow-coloured reverse. (e) Case 2: Maceration and desquamation on the left 3 rd and 4 th interdigital area. (f) Septate hyphae and intercalary chlamydoconidia (Parker ink-KOH, ×400). (g) Septate hyphae in the upper stratum corneum (Periodic acid-Schiff-stain, ×400). (h) Plate culture of Fusarium keratoplasticum, a white floccose colony with brown-coloured reverse. This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica. doi: 10.2340/00015555-3202 Acta Derm Venereol 2019; 99: 835–836