[Biological diagnosis of onychomycoses. Direct examination after simplified technique of PAS staining].

Confirmation of fungal origin of onychopathy by mycological examination is essential. For that purpose, in parallel to the cultivation of biological samples, achieving a sensitive and informative direct examination of nail fragments and subungual material is primordial. Among the direct examination techniques, and inspired from a technique of reference in histo-pathology (the "periodic acid-Schiff reagent" reaction), the simplified technique of PAS staining according to Hotchkiss and MacManus is the technique of choice. Easy to implement and very sensitive, it can immediately and formally confirm the diagnosis of onychomycosis, mention the type of fungus (yeast, dermatophyte, Hyphomycete opportunistic) and suspect a possible multiple involvement.