IDS and mucopolysaccharidosis: Taking into account some limitations of the study, represented by the limited number of patients, suffering from a disease that is clinically heterogeneous in terms of onset, severity and progression, the dynamic variation of expression levels observed for core clock genes and clock controlled genes in the fibroblasts of patients affected by HS at different time points of treatment with idursulfase may be an indirect evidence of the key role played by the molecular clock in the regulation of the complex array of cellular functions in this mucopolysaccharidosis.