We studied rhGAA uptake in fibroblasts from two mucopolysaccharidoses (MPS), Hunter disease (MPS II) and Maroteaux-Lamy disease (MPS VI), both characterized by generalized accumulation of glycosaminoglycans, and in mouse embryonic fibroblasts (MEFs) from a mouse model of multiple sulphatase deficiency (MSD), obtained by disruption of Sumf1 [25]. The gene discussed is SUMF1; the disease is mucopolysaccharidosis type 6.