Abstract
Onychomycosis is usually caused by dermatophytes, but some species of nondermatophytic molds and yeasts are also associated with nail invasion. Aspergillus niger is a nondermatophytic mold which exists as an opportunistic filamentous fungus in all environments. Here, we report a case of onychomycosis caused by A. niger in a 66-year-old female. The patient presented with a black discoloration and a milky white base and onycholysis on the proximal portion of the right thumb nail. Direct microscopic examination of scrapings after potassium hydroxide (KOH) preparation revealed dichotomous septate hyphae. Repeated cultures on Sabouraud's dextrose agar (SDA) without cycloheximide produced the same black velvety colonies. No colony growth occurred on SDA with cycloheximide slants. Biseriate phialides covering the entire vesicle with radiate conidial heads were observed on the slide culture. The DNA sequence of the internal transcribed spacer region of the clinical sample was a 100% match to that of A. niger strain ATCC 16888 (GenBank accession number AY373852). A. niger was confirmed by KOH mount, colony identification, light microscopic morphology, and DNA sequence analysis. The patient was treated orally with 250 mg terbinafine daily and topical amorolfine 5% nail lacquer for 3 months. As a result, the patient was completely cured clinically and mycologically.