NGF and erythema multiforme: In EM, NGF may affect the immune response by regulating the differentiation and survival of T and B cells; CYP17A1 can regulate estrogen levels to promote the proliferation of Tregs, thereby inhibiting the TGF-β signaling pathway or reducing the number of Tregs, which may help enhance the immune system’s ability to clear ectopic lesions (81–83).