LAUSR

Rhytidhysteron rufulum is a dematiaceous fungus that causes disease in plants, most commonly citrus and mangroves. Rare human infections are described, with previous cases exclusively in India. We report a case of phaeohyphomycosis caused by R. rufulum in a renal transplant patient in Tennessee, USA. A 40-year-old man presented with a painful, subcutaneous fluctuant nodule on his left dorsal hand. The patient had presented to another dermatologist with this nodule 1 month previously, at which time it had been incised and drained with a small amount of purulent drainage. A bacterial wound culture taken at that presentation was negative and no further antimicrobial therapy was initiated. The patient presented to our clinic because of rapid expansion of the nodule and increased pain. He had poorly controlled diabetes and he had received a living-donor renal transplant. Notably, he had been born in Ethiopia, but moved to the USA in 1995, at the age of 18 years. He last travelled outside the USA in 1998, and had never travelled to India. He did not recall any trauma to his hand. He was not currently employed and had no agricultural hobbies; however, he frequented a local Indian grocery store, where he bought all of his fruits, vegetables and grains. Physical examination demonstrated a pink to violaceous, peripherally firm, centrally fluctuant and crusted multilobular plaque, 25 9 20 mm in size, on the patient’s left dorsal hand (Fig. 1a). Two 4-mm punch biopsies were obtained and sent for histopathology and culture, to include bacteria, acid-fast bacilli and fungi. Histopathology demonstrated pseudoepitheliomatous hyperplasia with dermal fibrosis. Pigmented spores and hyphae were highlighted with Grocott–methenamine silver (Fig. 1b,c). Given the presence of both pigmented spores and hyphae, phaeohyphomycosis was diagnosed. Tissue cultures grew a dematiaceous mould 2 weeks later. This specimen was sent to a reference lab for identification, and DNA sequencing confirmed the presence of R. rufulum. Treatment was coordinated with the Transplant, Infectious Disease, Transplant Nephrology and Plastic Surgery departments. The patient was started on itraconazole 200 mg twice daily for 3 months, and underwent surgical excision of the lesion with the wound repaired by split-thickness skin graft. Phaeohyphomycosis is a mycelial dematiaceous fungal infection. Fungi causing this heterogeneous infection produce melanin pigment. They are differentiated histologically from chromoblastomycosis, a separate dematiaceous fungal infection, by the presence of pigmented hyphae and absence of sclerotic bodies. Genera commonly leading to phaeohyphomycosis include Curvularia, Alternaria, Bipolaris, Cladophialophora and Exophiala. Rhytidhysteron rufulum causing phaeohyphomycosis has only been described in reports from India, although R. rufulum can be found worldwide in both tropical and subtropical climes. Our patient did not recall any traumatic inoculation, but we postulate his infection may have been acquired via contact with fruits or vegetables at the Indian grocery store he frequented. Both immunocompromised and immunocompetent patients can be afflicted by R. rufulum phaeohyphomycosis. Morphologies include subcutaneous or ulcerative nodules, and in our case a multilobular plaque. The leg is most commonly affected in available reports. Treatment regimens have included itraconazole monotherapy and itraconazole in combinations with Correspondence: Dr Jonathan A. Braue, Department of Dermatology, Vanderbilt University Medical Center, 719 Thompson Lane, Suite 26300, Nashville, TN, USA E-mail: [email protected]