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Two Cases of Fungal Melanonychia

Summary

This paper describes two unusual cases where fungal infections of the toenails caused dark pigmentation (melanonychia). The first patient had a combination of two fungi (Aspergillus hiratsukae and Trichosporon faecale) causing black nail streaks, while the second had Exophiala xenobiotica and Trichophyton interdigitale causing dark-brown discoloration. Both patients were successfully treated with an antifungal medication called efinaconazole over several months.

Background

Onychomycosis (nail fungal infection) typically presents as white or yellowish turbid nails but can rarely present with dark-brown pigmentation called fungal melanonychia. This condition is caused by melanin pigment deposition from fungal infections, which can be either phaeohyphomycotic or non-phaeohyphomycotic in origin.

Objective

To report two cases of fungal melanonychia with identification of causative fungal species and treatment outcomes. The cases involve mixed fungal infections that had not been previously reported as causing melanonychia.

Results

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

Conclusion

Three of the four identified fungi (A. hiratsukae, T. faecale, and E. xenobiotica) had not been previously reported to cause fungal melanonychia, suggesting a wider variety of fungi may induce this condition than previously documented. Efinaconazole proved effective against both mixed infections, highlighting the importance of accurate fungal identification and antifungal susceptibility testing.
  • Published in:Acta Dermato-Venereologica,
  • Study Type:Case Report,
  • Source: PMID: 39560434, DOI: 10.2340/actadv.v104.42145
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