Dermatophytosis is an infection of the hair, skin, or nails caused by a dermatophyte, which is most commonly of the Trichophyton genus and less commonly of the Microsporum or Epidermophyton genera.Tinea capitis, tinea pedis, and onychomycosis are common dermatologic diseases that may result from such an infection.ermatophytosis is an infection of the hair, skin, or nails caused by a dermatophyte, which is most commonly of the Trichophyton genus and less commonly of the Microsporum or Epidermophyton genera.