Histopathologic evidence of the nondermatophytic mould Scopulariopsis brevicaulis masking the presence of dermatophytes in a toenail infection

Abstract

Nondermatophytic toenail infection with Scopulariopsis brevicaulis is rare, but may occur often in association with dermatophytes. We report a case of an 84-year-old man who presented with onychomycosis of the big toenail. Histopathologic examination of the avulsed nail showed evidence of S. brevicaulis coinfection with a dermatophyte, despite negative mycology results for the latter. Our case underscores the importance of histopathologic examination of nail specimens as an additional invaluable tool in the diagnosis of onychomycosis, as it may unmask false-negative mycology findings.

Update: nail unit dermatopathology

“…Onychomycosis can be caused by nondermatophyte fungal infection or coinfection with dermatophyte and nondermatophyte fungi (19,23). Several nondermatophyte fungi are resistant to standard therapies for onychomycosis, and therefore testing and culture for sensitivities should be considered.…”

“…7) (23). Stefanato and Verdolini reported a case of onychomycosis caused by Scopulariopsis brevicaulis disguising a dermatophyte infection.…”

“…Several nondermatophyte fungi are resistant to standard therapies for onychomycosis, and therefore testing and culture for sensitivities should be considered. In these cases, the nondermatophyte hyphae may be present in the nail plate on histologic exam whereas mycologic culture is negative (23). Culture plates use Sabaroud's destrose agar and may contain antibiotics such as cycloheximide that are intended to suppress contaminants such as nondermatophyte fungi (4).…”

“…On the histologic sections, the two fungi maintained separate boundaries, causing "territorial demarcation" between the infected regions (FIG. 7) (23).…”

PCR Detection of Scopulariopsis brevicaulis

“…Its prevalence is estimated to be 3-10% of total number of onychomycosis cases. The clinical manifestation is generally recognised as distal and lateral subungual onychomycosis (DLSO) (Stefanato and Verdolini, 2009;Gupta et al, 2012). There are also cases of smooth skin and sub cutaneous tissue infections caused by S. brevicaulis (Dhar and Carey, 1993;Bryuynzel and Starink, 1998;Anandan et al, 2008).…”