Onychomycosis (trichophyton mentagrophytes). A scanning electron microscopic observation.

Nails from four patients, infected with dermatophytes, were investigated with the scanning electron microscope (SEM) to gain insight into the spatial arrangements of the dermatophytes within the nail. Fungal hyphae could be detected in nails of all four patients. A toenail from one patient infected with Trichophyton mentagrophytes was more extensively studied and the results are presented in this paper. Light microscopic observations with bright field illumination and Nomarski interference contrast confirmed the dermatophytic infection. Fungal hyphae found with the SEM distally on the ventral part of the toenail showed typical T. mentagrophytes structures and the comparison with cultured material clearly demonstrated the correspondence in morphology and size. Besides the fine structural morphology of the invasion of fungal hyphae into the nail plate between the horny cells and/or directly into corneocytes, "tunnel"-like holes were observed in paraffin embedded sections after removal of the paraffin. Scanning electron microscopy, with its enormous focal depth, yielded far more information than light microscopic techniques about the three dimensional behavior of dermatophytes in the nail.