After 24 hours of treatment with idursulfase in fibroblasts of patients with Mucopolysaccharidosis type II the expression evaluated by NGS of the genes CLOCK, ARNTL2, NR1D1, NR1D2, and TIMELESS showed higher expression levels compared to untreated HS fibroblasts. The gene discussed is IDS; the disease is mucopolysaccharidosis type 2.