On the other hand, PFP have been associated with various systemic conditions, such as pernicious anemia [41,51,64,72,73], iron deficiency anemia [41], hemochromatosis [41,51,64,72,73], scleroderma [41,73,79], lichen planus [34,41], linear circumflex ichthyosis [34,41], hysteromyoma [34], and cystic hyperplasia [34]. This evidence concerns the gene PRF1 and lichen planus.