Arthroderma chiloniae spec. nov. isolated from human stratum corneum: description of a new Arthroderma species

A 68-year-old woman was submitted to our hospital for differential diagnosis of erythematous and scaly skin lesions. To exclude tinea samples of stratum corneum were collected and used for mycological investigations. In this material no fungal elements were detected microscopically, but after inoculation on Sabouraud agar with cycloheximide growth of a presumptive dermatophyte was noted. Meticulous investigations with conventional morphological and physiological methods and with genetic analyses revealed that this fungus was not identical with any known species of dermatophytes or related fungi. As a result we describe in detail a new Arthroderma (A.) species. Because of lacking specific macroscopic, microscopic and physiologic features genetic methods are necessary for its identification. Taxonomically it is most closely related to A. curreyi and A. eboreum based on a similarity of ITS1, ITS2 and 5.8S sequences of 78.5% and 79.7%, respectively.We have named it Arthroderma chiloniae because it was detected in Kiel. Our attempts to re-isolate this fungus from the patient’s skin over time failed although her skin lesions persisted. Most likely A. chiloniae is a geophilic species that in our case incidentally contaminated or transiently colonized the patient’s skin. To avoid diagnostic misinterpretations it is necessary to distinguish A. chiloniae from truly pathogenic dermatophytes like Trichophyton (T.) rubrum and T. interdigitale which can easily be confused with A. chiloniae due to their rather similar thallus morphologies.