Tinea incognito due to Trichophyton mentagrophytes

Unusual Species of Dermatophytes: Rarely Identified or New?

Dermatophytes are causing superficial mycosis in animals and humans. Depending on the geophilic, zoophilic or anthropophilic origin of the fungus but also on the immunological status of the patient, symptomatology can widely differ. Nevertheless, each species is currently associated with typical clinical manifestations, even if atypical localizations and/or clinical pictures are sometimes also reported. Diagnostic tools applied to species identification have been changing since the last two decades with the more frequent use of molecular methods currently considered nowadays as reference methods for species identification. It becomes obvious that the algorithm used for the distinction of closely related species needs to combine phenotypic and genomic methods. All these different points are discussed, and the most recent novel species causing or involved in human dermatophytosis are reported.

Tinea incognito due to microsporum gypseum

A 41-year-old woman presented with a pruritic rash on the face that was of 3 months duration. During that time, it had been successively misdiagnosed as psoriasis vulgaris, systemic lupus erythematosus, facial dermatitis at other hospitals, and had been treated with agents that included acitretin and prednisone. Finally, fungi were found in the lesions by optical microscopy, and the fungal culture was positive for Microsporum gypseum, and was diagnosed as a Microsporum gypseum infection. The lesions eventually cleared completely after 8 weeks of antifungal treatment.

Tinea incognito

Tinea incognito was first described 50 years ago. It is a dermatophytic infection with a clinical presentation modified by previous treatment with topical or systemic corticosteroids, as well as by the topical application of immunomodulators such as pimecrolimus and tacrolimus. Tinea incognito usually resembles neurodermatitis, atopic dermatitis, rosacea, seborrheic dermatitis, lupus erythematosus, or contact dermatitis, and the diagnosis is frequently missed or delayed.