Types of onychomycosis.

Onychomycosis may be classified into several types: distal subungual, white superficial, proximal subungual, endonyx, and total dystrophic. Distal subungual onychomycosis (DSO), the most common type, involves the nail bed and, subsequently, the nail plate. White superficial onychomycosis (WSO) usually manifests as superficial white patches with distinct edges on the surface of the nail plate. Proximal subungual onychomycosis results when the fungal organism enters via the cuticle and the ventral aspect of the proximal nail fold. In endonyx onychomycosis, fungal organisms invade the nail plate without resulting nail bed hyperkeratosis, onycholysis, or nail bed inflammatory changes. In total dystrophic onychomycosis, complete dystrophy of the nail plate occurs; these changes may be primary or secondary.