Usefulness of histological examination for the diagnosis of onychomycosis

Background: Direct microscopy and culture tests current ly used in the diag nosis of nail mycosis can yield false-negative results, and confirmation of the pathogenic agent, especially in non-dermatophyte infections, is often a lengthy process. Objective: The aim of this study was to investigate the usefulness of the histological examination of nail clipping samples in supp lementing the standard microscopic and culture techniques for the diagnosis of onychomycosis. Patients and Methods, One hundred and seventy-two subjec ts affected by nail alterations suggestive of onychomycosis were evaluated. Nail specimens were studied with 3 different techniques: direct microscopi c examination of a 40% KOH clarified preparation, fungal culture and histol ogical examination. Patients positive for fungal infection were reevaluated with the same techniques after treatment with oral terbinafine, fluconazol e or itraconazole and topical application of bifonazole or ciclopirox for 2 months. Results: Direct microscopy was positive in 102 (59.3%) nail specim ens. The culture test was positive in 90 cases (52.9%), showing a dermatoph yte in 45, a yeast in 23 and a mould in 22 samples. The histological examin ation was positive in 94 (54.6%) samples. In 4 cases, it was the only inves tigation confirming the clinical diagnosis of nail mycosis. In most of the cases, the morphological aspect of the hyphae and/or spores suggested also to which group of pathogens (dermatophytes, yeasts or moulds) the mycetes o bserved in the histological sections could be ascribed. The concurrent pres ence of a dermatophyte and a mould was evidenced in a few specimens. The co ntrol histological examination at the end of the treatment showed negative results or residual nonvital hyphae and/or spores. Conclusions: Results of the present study indicate that the histological examination of nail clippi ng specimens is a relatively inexpensive, rapid and easily performed proced ure. It is useful to confirm or refute the results of routine microscopy an d culture tests. Moreover, nail histopathological observation may help in a scribing a pathogenic role of non-dermatophyte isolates and evaluating the effectiveness of antifungal treatment. Copyright (C) 2001 S. Karger AG, Bas el.