Clinical, mycological and histological aspects of white onychomycosis.

Fungal leuconychia defines the clinical manifestations of white changes in onychomycosis. This uncommon clinical aspect is mostly seen, although not exclusively, in immunosuppressed patients. The principal isolated organism is Trichophyton spp. but the entity can also be caused by non-dermatophyte moulds. The mechanism of infection is unclear; it could be acquired through the proximal nail fold, or, as more recently proposed, may be secondary to lymphatic or vascular dissemination. To analyse the clinical, mycological and histopathological features of fungal leuconychia, we included 10 patients with the clinical diagnosis of fungal leuconychia. Direct examination of culture and nail plate biopsy were performed. Nine patients had confirmed fungal leuconychia. Four had a positive culture and all had positive haematoxylin-eosin (H&E) and Periodic Acid Schiff (PAS) stains for fungal elements with varying degrees of nail plate invasion. Seven of our patients were immunosuppressed and the isolated aetiological agents are the same as previously reported. The direct examination is reliable, fast and inexpensive to establish the diagnosis. The correlation of onychomycosis with histology, stained with H&E and PAS was 100%. We think that the site of nail plate invasion provides more information to support the theory that the infection reaches the ungual apparatus through systemic dissemination.