Treatment failures and relapses in onychomycosis: a stubborn clinical problem

Abstract

The therapeutic outcome of onychomycoses is uncertain. Comparative short-term efficacy studies on antifungals abound and report contradictory findings. Few unbiased follow-up studies have scrutinized the long-term outcome. Basically, none of the current antifungals can guarantee cure in all instances. In addition, relapses are not rare. The causes of therapeutic failure in onychomycoses are multiple. The most important are the lack of diagnostic accuracy, inadequate antifungal choice or delivery modality, and presence of dormant conidia, sequestrated mycelium pockets or resistant fungal species. The concept of fungicidal drug derived from selected in vitro studies appears irrelevant in clinical practice.