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Two Cases of Fungal Melanonychia

Summary

Two patients developed dark pigmentation on their toenails caused by rare combinations of fungal infections. Through laboratory testing and genetic analysis, doctors identified fungi never before known to cause this type of nail discoloration. Both patients were successfully treated with an antifungal medication called efinaconazole, with complete resolution of symptoms within a few months.

Background

Onychomycosis is typically caused by dermatophytes and presents as white or yellowish turbid nails. However, in rare cases, fungal infections can cause dark-brown pigmentation known as fungal melanonychia, which results from melanin pigment deposition from phaeohyphomycotic and non-phaeohyphomycotic infections.

Objective

This case report presents two cases of fungal melanonychia with mixed fungal infections to expand understanding of causative organisms and their mechanisms of melanin production.

Results

Case 1 identified mixed Aspergillus hiratsukae and Trichosporon faecale infection causing black longitudinal nail pigmentation, resolving after 120 days of 10% efinaconazole treatment. Case 2 identified mixed Exophiala xenobiotica and Trichophyton interdigitale infection causing dark-brown pigmentation, completely resolved after 173 days of efinaconazole treatment.

Conclusion

This report documents four fungi causing melanonychia, with three organisms (A. hiratsukae, T. faecale, and E. xenobiotica) never previously reported to cause this condition. The findings suggest a wider variety of fungi may induce fungal melanonychia through various melanin production pathways, and efinaconazole is effective against these causative organisms.
  • Published in:Acta Dermato-Venereologica,
  • Study Type:Case Report,
  • Source: PMID: 39560434, DOI: 10.2340/actadv.v104.42145
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