TLR4 and mucopolysaccharidosis: Indeed, significant overexpression of the Toll-like receptor 4 (TLR4) gene, the activation of interleukin-1 receptor-associated kinase 4 (IRAK4), in addition to numerous cathepsin proteases and matrix metalloproteinases were observed in MPS cardiovascular disease (Stepien et al., 2020) [38].