Fingernail Onychomycosis Due to Aspergillus niger

Area of Science:

• Mycology
• Dermatology
• Clinical Microbiology

Background:

• Onychomycosis is a common nail fungal infection, typically caused by dermatophytes.
• Nondermatophytic molds and yeasts, including Aspergillus species, are increasingly recognized as causative agents.
• Aspergillus niger is an opportunistic filamentous fungus found ubiquitously in the environment.

Observation:

• A 66-year-old female presented with clinical signs of onychomycosis on her right thumb, including black discoloration, milky white base, and onycholysis.
• Microscopic examination revealed dichotomous septate hyphae in potassium hydroxide (KOH) preparations.
• Fungal cultures yielded characteristic black velvety colonies of Aspergillus niger, confirmed by slide culture morphology and DNA sequencing.

Findings:

• Aspergillus niger was definitively identified as the causative agent of onychomycosis through a combination of KOH mount, culture, morphology, and DNA sequencing.
• The internal transcribed spacer (ITS) region DNA sequence of the clinical isolate showed a 100% match with Aspergillus niger ATCC 16888.
• The patient received a 3-month treatment regimen comprising oral terbinafine and topical amorolfine 5% nail lacquer.

Implications:

• This case highlights Aspergillus niger as a potential pathogen in onychomycosis, emphasizing the importance of accurate mycological diagnosis.
• Successful treatment outcomes demonstrate the efficacy of combined oral and topical antifungal therapy for Aspergillus niger onychomycosis.
• Further research into nondermatophytic mold onychomycosis is warranted to understand prevalence and optimize management strategies.