SMAD2 and polyostotic fibrous dysplasia: Previous studies have shown that PFD decreases the expression of TGFβ1 by blocking the expression of Smad proteins and activation of the TGFβ1/Smad2/3 signaling pathway, which enhances TGFβ1 transcription (Iyer et al., 1999; Choi et al., 2012; Sun et al., 2018; Lv et al., 2020).