Subcutaneous phaeohyphomycosis in a patient with IgG4-related sclerosing disease caused by a novel ascomycete, Hongkongmyces pedis gen. et sp. nov.: first report of human infection associated with the family Lindgomycetaceae

No members of the freshwater ascomycetes family Lindgomycetaceae have been associated with human infections. We isolated a mould (HKU35(T)) from the biopsy specimen of a patient with invasive foot infection and underlying immunoglobulin G4-related sclerosing disease. Histology showed florid, suppurative, granulomatous inflammation in the dermis, with central microabscess formation surrounded by epithelioid histiocytes, scattered giant cells, and a small number of lymphocytes. A Grocott stain revealed fungal elements in the center of the lesion. On Sabouraud glucose agar, HKU35(T) grew as gray and velvety colonies. Among the members of the family Lindgomycetaceae, HKU35(T) was the only strain that grew at 37 degrees C. Microscopically, only sterile mycelia, but no fruiting bodies, were observed. HKU35(T) was susceptible to itrazonazole, voriconazole, and posaconazole, which was in line with the patient's clinical response to itraconazole treatment. Internal transcribed spacer and partial 18S nuclear rDNA (nrDNA), 28S nrDNA, beta-tubulin gene, and EF1 alpha gene sequencing showed that HKU35(T) occupied a unique phylogenetic position, most closely related to but distinct from members of the genera Clohesyomyces and Lindgomyces. We propose a new genus and species, Hongkongmyces pedis gen. et sp. nov., to describe this fungus, which belongs to the family Lindgomycetaceae in the order Pleosporales of class Dothideomycetes. This case also represents the first report of human infection associated with the family Lindgomycetaceae.