Work

Molecularly confirmed neoscytalidium dimidiatum onychomycosis in an immunocompetent Iranian woman: a case report and comprehensive literature review

Year: 2026

Type: article

Abstract: Background Onychomycosis is one of the most common fungal infections of the nails and is predominantly caused by dermatophytes. However, non-dermatophyte molds (NDMs), including dematiaceous fungi, are increasingly recognized as clinically relevant pathogens. Neoscytalidium dimidiatum is an uncommon cause of onychomycosis, reported predominantly in tropical and subtropical regions, although cases from temperate settings have also been described. Case presentation We report a case of distal and lateral subungual onychomycosis (DLSO) caused by N. dimidiatum in a 54-year-old immunocompetent Iranian woman without underlying systemic disease or immunosuppressive therapy. She presented with progressive discoloration and dystrophic changes of a toenail following previous trauma. Direct microscopy of nail specimens using potassium hydroxide (KOH) demonstrated septate, branching fungal hyphae with occasional pigmentation. Culture on Sabouraud dextrose agar yielded a rapidly growing melanized-mold with characteristic dark pigmentation. Given the phenotypic overlap among Neoscytalidium species, molecular identification was performed. Internal transcribed spacer (ITS) rDNA sequencing identified the isolate as N. dimidiatum , with more than 99% sequence identity to reference sequences. The patient received combination therapy with oral itraconazole, amorolfine 5% nail lacquer, and topical sertaconazole 2%, with marked clinical improvement after 3 months; mycological cure remained under evaluation. Conclusion This case contributes to the limited literature on N. dimidiatum onychomycosis by documenting molecularly confirmed DLSO in an immunocompetent Iranian woman and demonstrating concordant clinical, mycological, and molecular findings. It highlights the diagnostic challenges of NDM onychomycosis and supports an integrated approach combining direct microscopy, culture, and molecular identification for accurate species-level diagnosis and appropriate clinical management.

Source: IDCases

DOI: 10.1016/j.idcr.2026.e02812