Onychomycosis Caused by Chaetomium globosum
A 35-year-old male presented with a 2-year history of brownish-yellow discoloration and subungual hyperkeratosis on the right toenails (1st and 5th) and left toenails (1st and 4th) (, ). The patient was otherwise in good health and he denied nail trauma or dystrophic nail abnormalities prior to the onset of the present lesions. There was no history of other diseases except for toenail dystrophy. On the visit, laboratory studies including a complete blood cell count with differentials, liver and renal function test, venereal disease research laboratory, urinalysis, stool examination, hepatitis viral test, human immunodeficiency virus test, chest X-ray, and electrocardiogram were all within normal limits or negative.\nIn mycological examination, septated hyphae were observed in 20% KOH preparation from the toenail lesions. Nail specimens were cultured on two Sabouraud's dextrose agar (SDA) without cycloheximide slants at 25℃ for a week to yield several identical colonies. However, there was no growth of colony on SDA with cycloheximide slants. These rapid growing colonies were initially velvety white then turned to dark gray to brown (). The reverse surface of the colonies revealed an orange-tan color. Subcultures on agar plates exhibited the same results (, ). When the slide cultures of fungal colonies were stained with lactophenol cotton blue, the morphological characteristics such as brown-colored septated hyphae, perithecia and ascospores were observed by light microscopy (). Perithecia were large and dark brown to black color, revealing a globose to flask shape with unbranched, hair-like filamentous appendages on their surface. Perithecia demonstrated ostioles and contained asci and single-celled ascospores which were olive brown and lemon-shaped (, ).\nThe ITS region of ribosomal RNA genes was amplified using DNA of the fungal colonies cultured from nail specimens. For molecular biologic analysis, DNA was extracted from the cultured colonies and the base sequence of ITS was identified. Subsequently, it was compared to the base sequence of C. globosum strain ATCC 6205 (GenBank accession number: EF524036.1), which was stored in GenBank, using the Blast program. The result was 100% matched ().\nBased on the KOH mount, mycological finding, light microscopy and sequence analysis of the ITS region, the isolate was finally identified as C. globosum. The patient was treated with 250 mg oral terbinafine daily and topical amorolfine 5% nail lacquer for 3 months.