To understand whether the increase in autophagic markers observed in MPS VI cells is due to the deficient ability of lysosomes to recycle metabolites, we compared the Epidermal Growth Factor (EGF)/EGF Receptor (EGFR) turnover in MPS VI and NR fibroblasts based on the knowledge that binding of EGF to EGFR induces ubiquitination, rapid internalization and degradation of both ligand and receptor via the lysosomal pathway [25,26]. This evidence concerns the gene EGFR and mucopolysaccharidosis type 6.