Superficial white onychomycosis--a syndrome with different fungal causes and paths of infection.

Superficial white onychomycosis (SWO) is a clinical term used to describe onychomycosis in which the invasion of the nail plate occurs from the dorsal surface. However, recent observations indicate that the clinical appearances may vary to include infection in patches or in a striate patter. This report shows that, in some cases, it may be combined with either distal and lateral subungual onychomycosis or proximal white subungual onychomycosis. Invasion of the dorsal nail surface, but originating from the proximal nail fold, is another route of infection in SWO. A new classification of this condition is proposed with 4 main variants. Although based on clinical features, often other factors such as immunosuppression or invading organism (eg, Trichophyton rubrum or Fusarium species) appear to play a role in the development of a particular pattern of infection. This is an observational study carried out by trained and experienced clinicians. The main clinical implication is that in combined forms, or where the infection emerges from beneath the proximal nailfold, systemic rather than topical antifungal therapy is advised.