TLR4 and mucopolysaccharidosis: A possible link between early neuroinflammation and oxidative stress in patients with MPS is represented by GAGs degradation products, which being structurally similar to lipopolysaccharide (LPS)—an endotoxin of Gram-negative bacteria product—may bind and activate the Toll-Like Receptor 4 (TLR4), thus leading to pro-inflammatory cytokine release and innate immune system activation [23].