Trichothiodystrophy 4, Nonphotosensitive, also known as amish brittle hair brain syndrome, is related to trichothiodystrophy 1, photosensitive and trichothiodystrophy, and has symptoms including koilonychia An important gene associated with Trichothiodystrophy 4, Nonphotosensitive is MPLKIP (M-Phase Specific PLK1 Interacting Protein). Affiliated tissues include brain and skin, and related phenotypes are nystagmus and short nose