Neoscytalidium dimidiatum as onychomycosis causative agent in an Iranian patient: a case report and literature review

A 38-year-old healthy male presented to our medical mycology center with whitish opaque discoloration of the right toenail. He reported a history of some sand scratches subsequent to walking barefoot on the beach two years ago and wearing hard safety shoes for a period of two years. On clinical examination, onycholysis, onychodystrophy, and apparent thickening of the ungual bed in the left big toe were found. The microscopic examination of nail clippings using 15% potassium hydroxide (KOH/) revealed the presence of septate pigmented hyphae. The fungus was identified as Neoscytalidium dimidiatum based on the cultural characteristics, the arrangement of arthroconidia on lactophenol cotton blue (LPCB) staining, blocky-brown pigmented hyphae on serum physiology mounts, and sequencing. Susceptibility of the isolated fungi to amphotericin B, itraconazole, voriconazole, and terbinafine was tested using the standard broth microdilution M38-A2 method developed by the Clinical and Laboratory Standards Institute (CLSI). The minimum inhibitory concentrations (MICs) of the four antifungal drugs used in this study were: amphotericin B: 1 mg/L, itraconazole: 2 mg/L, voriconazole: 0.25 mg/L, and terbinafine: 1 mg/L. The patient underwent terbinafine and clobetasol topical treatments for 6 months.