The Brief Case: A case of tinea corporis caused by drug-resistant Trichophyton indotineae identified by broad-range fungal DNA sequencing

A 36-year-old woman presented to dermatology with a several-month history of a pruritic, burning, and bleeding rash involving the lower abdomen, thighs, geni talia, and perineum that began after traveling to India (Fig. 1A and B).She had no known history of HIV or immunosuppression.Other medical, surgical, and social history was non-contributory.She had been prescribed oral fluconazole, topical clobetasol 0.05% cream, and terbinafine 1% cream without improvement.Dermatologic exam and in-office microscopic examination of skin scraping with potassium hydroxide (KOH) revealed septate hyphae, consistent with tinea corporis.The patient was instructed to stop clobetasol, and was prescribed terbinafine 250 mg daily for 3 weeks, topical terbinafine 1% cream, and oral hydroxyzine for pruritus.On follow-up, she reported improvement during the first week of treatment, but the rash continued to progress significantly.Two biopsies were taken from the mons pubis and left medial thigh, which confirmed a diagnosis of tinea corporis.She was prescribed oral itraconazole 200 mg daily for 3 weeks with sparing use of desonide 0.05% cream.After 4 weeks, she had approximately 60% improvement but still had extensive, spreading dermatitis.She was prescribed a repeat course of itraconazole 200 mg daily for 3 weeks, ketoconazole 2% cream, and nystatin powder.Another month later, she had persistent tinea infection and secondarily progressing lichen simplex chronicus.Sterile punch biopsy for fungal culture was collected and itraconazole dosing was increased to 200 mg twice daily for 3 weeks.She was instructed to avoid over-the-counter antacids and take the itraconazole with orange juice for adequate absorption.The patient reported only taking 1 week of the increased itraconazole dose and her infection continued to progress.Repeat biopsy was obtained for fungal culture.She was started on griseofulvin microsize 500 mg daily for 8 weeks.The left thigh punch biopsy showed dermatophytes in the stratum corneum (Fig. 1C), which was confirmed by PAS stain (Fig. 1D).The formalin-fixed paraffin-embedded biopsy was also sent to the University of Washington Molecular Microbiology laboratory for direct specimen broad-range fungal PCR targeting the large ribosomal subunit gene (28S rRNA) and internal transcribed spacer region (ITS) (1).The ITS sequence obtained (Genbank accession PP317116) was compared to well-characterized T. mentagrophytes/T.interdigitale complex sequences previously analyzed by Uhrlaß et al. (2).These formed a well-supported clade with genotype VIII records (>80% bootstrap support), consistent with T. indotineae (Fig. 2) (2).This clade also contained one record each currently annotated as genotypes XIII and XIV, which were previously suggested to represent T.