Unexpected Perseverance in Tinea Corporis – Special Mutations Found in <i>Trichophyton indotineae</i> Dermatomycosis

ABSTRACT We hereby present the case of a patient with tinea incognita, who had received treatment with glucocorticosteroids and antibiotics for several months. Further diagnostic testing identified Trichophyton indotineae as the pathogen causing tinea corporis and cruris. The Erg1 gene encoding squalene epoxidase showed wild‐type information; therefore, we treated systemically with terbinafine. We observed a prolonged course of the disease despite systemic treatment with terbinafine. After the initial clinical response, new lesions occurred in which mycologic testing revealed T. indotineae again, and expression analyses showed upregulation of MDR transporter genes and heat shock proteins HSP60 and HSP90 in the isolate obtained from the relapse. These findings suggest a better adaptation to body temperature and increased efflux of antifungals. The relapse isolate showed increased inhibitory concentrations for terbinafine, accompanied by decreased values for itraconazole. We obtained mycologic cure by systemic itraconazole and topical miconazole nitrate. This case highlights the importance of mycologic diagnostics through quantitative Real‐Time PCR, including assessment of more than just the ergosterol ( Erg ) biosynthesis genes. It raises consciousness about tinea incognita and the ever‐emerging threat of terbinafine‐resistant dermatomycoses.