Xanthothecium peruvianum isolated from human stratum corneum: A case report, characterisation and short review that suggest emendation of Arachnomyces peruvianus

Abstract

From stratum corneum samples of a palmar eczema, a fungus was isolated that developed white colonies with a yellowish dark reverse, suggestive of dermatophytes. The isolate produced numerous chlamydospores and sparse aleuroconidia, was resistant to cycloheximide, grew well on human stratum corneum samples and was positive in tests for urease production and hair perforation, but no dermatophyte could be identified. After several weeks, cleistothecia with delicate asci and disc-shaped ascospores were formed, suggesting Arachnomyces spp. The analyses of the ribosomal ITS and LSU (D1/D2 domains) nucleotide sequences proved a good match with the ex-type strain of Xanthothecium peruvianum (family Onygenaceae, order Onygenales), and LSU sequence showed 99% similarity with Arachnomyces glareosus. This is the first report of X. peruvianum isolated from human skin. The description of our isolate provides new information about this species and proposes its transfer to the genus Arachnomyces with the subsequent emendation of the description of Arachnomyces peruvianus. Morphologically and physiologically it mimics dermatophytes and other species of the genus Arachnomyces. Although the clinical situation did not suggest any relevance for A. peruvianus as a primary pathogen, this fungus may act as a secondary pathogen under suitable conditions due to its keratinolytic capacity.

Keywords: Ascomycota; DNA; ITS; Onygenales; dermatitis; fungi; keratin.