Onychomycosis caused by an isolate conforming to the description of Trichophyton raubitschekii.

Trichophyton raubitschekii is currently regarded as a synonymous name betokening a variant form of Trichophyton rubrum. Nonetheless, isolates conforming to this morphotaxonomic concept have morphological, physiological and clinical features very different from those of typical T. rubrum. Isolates are mainly obtained from subjects originating from certain tropical and subtropical countries, and are mainly obtained from upper body skin infections, rarely from onychomycosis. In this paper the authors report the first known Italian case of onychomycosis caused by such an isolate. The patient, a male student from Cameroon, had a typical fingernail tinea unguium, without any other sign of skin or nail infection. 'T. raubitschekii' was identified on morphological and physiological grounds by the following features: velvety colony surface, brownish pigment, abundant macroconidia and microconidia, and positive urease activity. Such isolates may prove very difficult to identify correctly, especially in areas like Italy where T. rubrum is normally seen only as isolates presenting a strongly differing phenotype.