Deep dermatophytosis: rare infections or common, but unrecognised, complications of lymphatic spread?

The mechanisms limiting spread of dermatophyte fungi, under normal circumstances, to the epidermis remain elusive. The hypothesis linking a specific clinical form of dermatophyte nail infection with lymphatic spread, although intriguing, needs verification. In particular, it is important to clarify whether viable dermatophytes can be detected outside the epidermis or nail plate and whether they will then remain viable and provide a source of endogenous re-infection. It is clear that wider internal dissemination of dermatophyte fungi can occur, but is a rare event. Hence there is still some doubt as to whether the mysterious arrival of dermatophytes in the proximal nail fold, particularly in immunosuppressed patients, is a sign of lymphatic dissemination or whether we should still be searching for another portal of entry.