[Fungi causing onychomycoses in The Netherlands]

To obtain information about prevalences of fungi responsible for onychomycosis in the Netherlands.

Retrospective.

Mycological laboratory of the Dermatological department, University Hospital, Leiden, the Netherlands.

The results of mycological tests of nail samples collected in the period of 1987-1992 were analysed. If the culture was positive, the nature of the yeast or dermatophyte was determined.

Nail samples were obtained from 861 patients (22% fingernails, 78% toenails). No mycological confirmation of clinical diagnosis could be obtained in 60% of fingernail samples and 45% of toenail samples. Of the mycologically confirmed finger onychomycoses 77.5% were caused by yeasts, the remaining part by Trichophyton rubrum. Toenail onychomycosis in 9.9% of the cases was caused by yeasts, in 11.8% by T. mentagrophytes, in 1.2% by Epidermophyton floccosum, and in under 1% by non-dermatophytes. Just as in fingernail onychomycosis, the major cause of toenail onychomycosis is T. rubrum.

Onychomycosis cannot be diagnosed on clinical grounds, without mycological testing. Since antimycotic treatment is not always effective in onychomycosis caused by yeasts and non-dermatophytes, mycological diagnosis is necessary.