Review of epidemiological data for onychomycosis caused by Aspergillus spp.
June 04 2018
Fungal infections of the nail apparatus (onychomycosis) are common, accounting for about 50% of all nail disorders and an estimated global burden of ~300 million cases. Dermatophytic moulds of the genera Trichophyton, Epidermophyton and Microsporum are the aetiologic agents in over 75% of cases. Yeasts and nondermatophyte (saprophytic) moulds (NDM) such as Aspergillus spp., Scopulariopsis spp., Alternaria spp., Acremonium spp. and Fusarium spp. have been previously reported to be responsible for approximately 2-25% of all the causes of onychomycoses
Aspergillus spp. are emerging causative agents of NDM onychomycosis. A recent critical review by Dr Felix Bongomin and colleagues extracted data from 42 epidemiological studies and showed that onychomycosis due to Aspergillus spp. varies between <1 and 35% of all cases of onychomycosis in the general population, and even higher among diabetic populations (up to 71%) and the elderly. However, >70% of patients with Aspergillus onychomycosis did not have identifiable risk factors and it is very uncommon among children and adolescence. Aspergillus spp. constitute 7.7–100% of the proportion of NDM onychomycosis, with the toenails being involved 25 times more frequently than fingernails.
Distal-lateral subungual onychomycosis is the most common clinical presentation caused by Aspergillus spp., with A. niger and A. fumigatus being the commonest species. Aspergillus spp. never affects the skin surrounding the nail (unlike dermatophytes).
A positive direct microscopy, and repeated culture or molecular detection of Aspergillus spp. is sufficient to diagnose Aspergillus onychomycosis, provided no dermatophyte was isolated. Systemic antifungal treatment with either terbinafine or itraconazole is adequate, usually with good clinical response. However, toenail discolouration may persist even after mycological cure.