Onychomycosis by Paecilomyces lilacinus

Area of Science:

• Mycology
• Dermatology
• Infectious Diseases

Background:

• Onychomycosis is a common fungal infection affecting toenails and fingernails.
• Paecilomyces lilacinus is an opportunistic fungus rarely implicated in human infections, particularly onychomycosis.
• Documenting rare etiological agents of onychomycosis is crucial for understanding disease spectrum and treatment challenges.

Observation:

• An 81-year-old Caucasian woman presented with clinical signs of onychomycosis on her first left toenail.
• Clinical presentation included yellow-brown discoloration, distal-lateral onycholysis, and subungual hyperkeratosis.
• Microscopic examination revealed irregular hyphae, and cultures yielded characteristic lilac, powdery colonies of Paecilomyces lilacinus.

Findings:

• The causative agent was identified as Paecilomyces lilacinus through culture and microscopic analysis of nail samples.
• The infection demonstrated resistance to common antifungal therapies, including amorolfine nail lacquer, itraconazole, and terbinafine.
• This case represents the sixth reported instance of Paecilomyces lilacinus onychomycosis globally and the second in Italy.

Implications:

• This case highlights the potential for Paecilomyces lilacinus to cause refractory onychomycosis.
• It underscores the importance of accurate mycological diagnosis for identifying uncommon fungal pathogens.
• Further research into effective treatment strategies for Paecilomyces lilacinus onychomycosis is warranted.