Unusual fungal species causing onychomycosis


Olga López-Jodra y Josep M Torres-Rodríguez
Rev Iberoam Micol 1999; 16: S11-S15


Dermatomycoses caused by non-dermatophytic mycelial fungi are very rare withthe exception of onychomycoses. Controversies regarding the pathogenic roleoften arise when these species and yeasts are isolated from nail scrapings.Candida albicans and Candida parapsilosis are the species identified more frequentlyfrom nails, particularly from finger nails. Because they could be residentflora of the skin, cultures should be interpreted according to clinical data, directmicroscopic observation of clinical samples, and quantification of colonies. Therecognition of other yeasts, such as Candida guillermondii, Candida famata orCandida krusei is more problematic. Isolation of moulds form toe nails accountsfor 2 to 12% in different studies, with a prevalence of 7.6% in Barcelona beingScopulariopsis brevicaulisthe most frequent species, but Aspergillus versicolorisalso a particular etiologic agent of onychomycosis (2.5%). To confirm the etiologyof any onychomycosis, standard criteria for mycological diagnosis and identificationof moulds should be strictly applied. Experience in the diagnosis of superficialmycosis due to new species of fungi is required for improving currentknowledge on the prevalence and clinical importance of this type of infections.