Several microorganisms (bacteria, fungi, etc.)have been implicated as triggers capable of initiating or exacerbating psoriasis 39, 40, 41, 42, among which LPS and peptidoglycan of Gram‐negative bacteria could be ligands of TLR4 on HEKs and further up‐regulate the TLR4 expression 33. This evidence concerns the gene TLR4 and psoriasis.