Non-dermatophyte mould onychomycosis (NDMO) is an opportunistic fungal nailinfection (onychomycosis) caused by moulds.
Moulds are ubiquitous in the environment, and thus are common contaminants that grow in nail fungal culture. Most moulds are non-keratolytic (except for Neoscytalidium dimidiatum) and require the presence of underlying trauma or other nail disease to penetrate the nail.
Mould infections
Aspergillus infection
Fusarium infection
Fusarium infection
Who gets non-dermatophyte mould onychomycosis?
Non-dermatophyte mould onychomycosis constitutes approximately 10% of onychomycosis cases globally. Recent reports suggest a rise in prevalence, especially cases presenting with a dermatophyte co-infection.
Risk factors identified for NDMO are similar to those for onychomycosis as a whole.
Infection may also lead to various nail colour changes depending on the infecting species. For example, infection with Aspergillus niger typically results in a black nail colour.
What are the complications of non-dermatophyte mould onychomycosis?
Total dystrophy of nail
Secondary bacterial infection
How is non-dermatophyte mould onychomycosis diagnosed?
As most moulds require the presence of an underlying nail condition to penetrate the nail, definitive diagnosis can be challenging.
The following diagnostic criterion has been established and the presence of 3 or more of the following criteria confirms diagnosis:
Positive direct microscopy
Absence of a dermatophyte in culture
Growth of non-dermatophyte mould in culture
Similar growth of the causative agent in repeat culture
Positive inoculum count
Positive histology.
Recent diagnostic advances for non-dermatophyte onychomycosis include molecular diagnostics using PCR technology.
What is the treatment for non-dermatophyte mould onychomycosis?
Mould infections are more difficult to clear than dermatophyte infections and may require a combination of topical and oral therapies to clear the fungal infection.
Systemic therapy such as itraconazole or terbinafine either as daily dosing or in a pulse regimen (often combined with topical treatment as above).
Other modalities
Medical nail avulsion (chemical or surgical) or debridement in combination with antifungal agents as per above.
What is the outcome for non-dermatophyte mould onychomycosis?
Non-dermatophyte mould onychomycosis often requires a longer duration of treatment compared to treatment for dermatophyte nail infection. The possibility of relapse is also higher.
Bibliography
Gupta AK, Drummond-Main C, Cooper EA, Brintnell W, Piraccini BM, Tosti A. Systematic review of nondermatophyte mold onychomycosis: diagnosis, clinical types, epidemiology, and treatment. J Am Acad Dermatol. 2012;66(3):494–502. doi:10.1016/j.jaad.2011.02.038. Journal
Gupta AK, Summerbell RC, Venkataraman M, Quinlan EM. Nondermatophyte mold onychomycosis. Journal of the European Academy of Dermatology and Venereology. 2021 Mar 24. Journal
Bongomin F, Batac CR, Richardson MD, Denning DW. A review of onychomycosis due to Aspergillus species. Mycopathologia. 2018 Jun 1;183(3):485–93. Review
Gupta AK, Taborda VB, Taborda PR, Shemer A, Summerbell RC, Nakrieko KA. High prevalence of mixed infections in global onychomycosis. PloS one. 2020 Sep 29;15(9): e0239648. Journal