SWO is also nearly always due to a dermatophyte
infection, most commonly T. mentagrophytes. It is much
less common than DLSO and affects the surface of the
nail plate rather than the nail bed. Discoloration is
white rather than cream and the surface of the nail
plate is noticeably flaky. Onycholysis is not a common
feature of SWO and intercurrent foot infection is not as
frequent as in DLSO.