Accordingly, the evaluation by qRT-PCR of clock gene expression upon synchronization through serum shock of normal fibroblasts and fibroblasts of patients affected by Hunter syndrome before and after 24 hours of idursulfase treatment evidenced a statistically significant effect on the expression levels of ARNTL2, PER1 and PER2, but only at the earlier time points examined, with advance of the phase of oscillation of gene expression. This evidence concerns the gene PER2 and mucopolysaccharidosis type 2.