Cutaneous hyalohyphomycosis caused by Fusarium subglutinans

ARTICLE

Auteur(s) : Qiu Xia Chen¹, Chang Xing Li², Wen Ming Huang¹, Jiang Qiang Shi¹, Shun Fang Li¹

¹Department of Dermatology, The affiliated hospital of Guangdong Medical College, Zhanjiang 524001, PR of China
²Department of Dermatology, Dongguan Institute of Dermatology, NO.216 Dongcheng West Rd., Dongguan 523008, PR of China

Cutaneous hyalohyphomycosis is an unusual opportunistic mycotic infection, where the tissue morphology of the causative organism is mycelial [1]. We report a case of cutaneous hyalohyphomycosis due to F. subglutinans, successfully treated with oral terbinafine.

A 72-year-old female farmer who frequently worked barefoot on soil presented with a 3-year history of an ulcer on her right ankle. She suffered erythema on her right ankle after a mosquito sting 3 years previously. Over a 6-month period, this erythema evolved into an ulcer. Two weeks before presentation, her condition worsened with pain in her leg. There was no history of any trauma preceding the illness. There was no history of tuberculosis, diabetes, or exposure to venereal diseases and HIV. Laboratory findings, including full blood count, urinalysis, peripheral blood smear, liver and renal function tests, were within normal limits. Physical examination showed mild edema of the right lower extremity with ulceration on the left side of the right ankle measuring about 3 cm × 1.5 cm in diameter (figure 1A). There were no varicose veins and the genitalia were normal. Systemic examinations were normal. A histological section of the biopsy material stained with periodic acid-Schiff and HE stains showed a hyperplasic epidermis. The dermis showed an extensive granulomatous reaction with central necrosis, granulomatous infiltrate with giant cells and the presence of septate hyphae (figure 1B). Periodic acid Schiff staining confirmed the presence of spores (figure 1C). Septate branched hyaline hyphae were observed in KOH preparation from the skin lesions of the right ankle. The specimens of skin biopsy cultured on Sabouraud's dextrose agar (SDA) at 27 °C yielded pink colonies (figure 1D) measuring 3.9 cm in diameter after 6 days incubation and were subsequently cultured on the potato dextrose agar (PDA) at 27 °C. After 48 hours, microscopy revealed aerial mycelium, being septate, branched, hyaline micoconidia in false heads or aerial mycelium (figure 1E). Macroconidia are three to five septate and produced in the aerial mycelium as well as from branched conidiophores in sporodochia.

The case isolate was tested to determine susceptibility to antifungal drugs. Tests were carried out by a previously described microdilution method, performed according to the Clinical and Laboratory Standards Institute (CLSI) for yeasts [2], using RPMI 1640 medium. The MIC values determined at 2 intervals (at 48 and 72 h after incubation, respectively) were as follows: for amphotericin B, 1.0 and 1.0 μg/mL; for ketoconazole, 16.0 and 16.0 μg/mL; for terbinafine, 1.0 and 1.0 μg/mL; for itraconazole, 16.0 and 32.0 μg/mL; for miconazole, 16.0 and 16.0 μg/mL.

Oral terbinafine (250 mg daily) was administered. Within 2 weeks the ulcer healed significantly. After 8 weeks of therapy, the lesions cleared and there was no clinical sign of infection (figure 1F), and the therapy was then discontinued. There was no recurrence after 6 months follow-up.

Fusarium infections in humans most frequently involve keratitis, onychomycosis, and superficial infections of the skin in patients with burns and surgical wounds [3-6].

In our patient, the diagnosis of hyalohyphomycosis was confirmed by mycological and pathological evidence. Although she was immunocompetent, she had been stung by a mosquito and, as a farmer, might have had repetitive fungal contact with her leg. The optimum therapy of F. subglutinans infection is unclear because of the lack of reported cases. Antifungal susceptibility tests of the isolate from the patient demonstrated a high sensitivity to terbinafine. The lesions cleared within 8 weeks, although the treatment time is too short for this infection by Fusarium spp. We suggest that terbinafine combined with topical 1/8000 potassium permanganate solution may be a promising alternative therapy for cases of subcutaneous hyalohyphomycosis due to F. subglutinans infection.

Acknowledgements

References

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