Tinea unguium is a fungal invasion caused by dermatophytes. Distal subungual infection is one of the common patterns of nail invasion and generally involves the nail bed and the underside of the nail in the distal portion. A mild inflammation produces hyperkeratosis and focal parakeratosis causes lifting of the nail plate and its detachment from the nail bed. Trichophyton rubrum, Trichophyton mentagrophytes and Epidermophyton floccosum are the main three agents of tinea unguium. Dignosis is confirmed by mycologic study with direct observation and a positive culture. Laboratory tests (KoH microscopy, culture, PAS) show variable results with regard to reliability and predictive value.