Nail Histomycology, Onychochromobiology, and Fungal Thigmatropism

Background: Thigmotropism is a biologic feature coping with the directional growth of cells following topographical guidance cues. This mechanism is involved in the invasive phase of pathogen and opportunistic fungi. It was shown experimentally with fungal hyphae of both dermatophytes and nondermatophyte molds, as well as with the mycelial phase of the dimorphic yeast Candida albicans. Objective: To revisit histomycology in onychomycoses of a diversity of fungal origins. Method: Histopathological section of nails plates were oriented parallel to the nail direction of growth. Result: Thigmotropism in part explains the patterns of orientations and shapes of fungi invading nail plates. It is probably influenced by onychochronobiology (speed of growth of the affected nails), and it governs various clinical presentations of onychomycoses.