SMAD4 and abscess: Except for the injection history, GF is also related to other factors such as scar constitution, poliomyelitis, history of abscesses in buttocks, idiopathic GMC, cytokines (e.g., TGFβ-1, β-3, Smad4, and sphingosine-1-phosphate), immune function abnormalities, physical relationship, as well as children’s susceptibility factors, character factors, gender factors and genetic factors [1, 16–18].