Opportunistic toenail onychomycosis. The fungal colonization of an available nail unit space by non‐dermatophytes is produced by the trauma of the closed shoe by an asymmetric gait or other trauma. A plausible theory

Abstract

Opportunistic onychomycosis is defined, when a non-dermatophyte mould is cultured from an abnormal nail unit in the absence of a dermatophyte. The presumption is that the mould has caused the abnormal clinical appearance of the nail unit, yet there are no data available to substantiate this claim. Reports have only identified the mould being recovered from the nail unit niche. A review of the published dermatologic literature describing toenail opportunistic onychomycosis by non-dermatophyte fungi has shown toenails with onycholysis, nail bed (NB) keratosis and nail plate surface abnormalities. The appearance of these clinical changes is indistinguishable from the diagnosis of the Asymmetric Gait Nail Unit Signs (AGNUS). AGNUS is produced by the friction of the closed shoe in patients with an asymmetric gait, resulting primarily from the ubiquitous uneven flat feet. Most commonly, species of Acremonium (Cephalosporium), Aspergillus, Fusarium, Scopulariopsis and rarely species of many different fungi genera are capable of surviving and reproducing in a keratinous environment and change the clinical appearance of the involved nail unit. AGNUS toenails predispose to the colonization by the non-dermatophyte opportunistic fungi but not by dermatophyte fungi.

The prevalence of unsuspected onychomycosis and its causative organisms in a multicentre Canadian sample of 30 000 patients visiting physicians' offices

“…Recently, asymmetric gait nail unit syndrome (AGNUS) has been discussed as a clinically similar condition to onychomycosis, without fungal infection being present. 10,11 Patients in our study with abnormal nails in the absence of Prevalence of onychomycosis positive culture (Table 3) may be presenting with AGNUS. The prevalence of onychomycosis reported here, however, is based on mycological confirmation.…”

“…It is worth noting that clinically diagnosing DLSO or other presentations without mycological confirmation may inflate prevalence of onychomycosis. Recently, asymmetric gait nail unit syndrome (AGNUS) has been discussed as a clinically similar condition to onychomycosis, without fungal infection being present . Patients in our study with abnormal nails in the absence of positive culture (Table ) may be presenting with AGNUS.…”

Aspergillus species: An emerging pathogen in onychomycosis among diabetics

“…Diabetic patients more than 50 years old are more susceptible to fungal infections in toenails due to diminished blood circulation, increased thickness of the nail plate, decreased the growth rate of the nail, and poor foot hygiene. [ 19 ]…”

“…[ 20 ] Aspergillus onychomycosis starts at the tip of the underside of the nail, where spores get accumulated, and the infection spreads toward the cuticle and the nails become thick, discolored, and flaky. [ 19 ]…”

Non‐dermatophytic onychomycosis diagnostic criteria: an unresolved question

“…It has not been fully established whether non‐dermatophyte infections occur as a primary event on healthy nails or can only affect nails already damaged by ischemia, trauma or other diseases . Recently published literature describing toenail opportunistic onychomycosis by NDMs have shown that an asymmetric gait or other trauma as well as health conditions such as diabetes and psoriasis predispose the NDMs nail colonisation.…”