Mucopolysaccharidoses (MPSs) are a group of chronic, progressive lysosomal storage diseases (LSDs) with multi-system impairments. They are rare genetic disorders with a combined incidence of approximately 1 in 25,000 live births (Tomatsu S et al 2013) and the most common type is MPS II followed by MPS I, III, IV, VI and VII (Khan SA et al 2017). These disorders are caused by an enzyme deficiency resulting in the inability to break down glycosaminoglycans (GAGs; formerly called mucopolysaccharides) into smaller sugar molecules. Glycosaminoglycans in lysosomes include chondroitin sulfate, dermatan sulfate, heparin sulfate, keratin sulfate and/or hyaluronan. An enzyme deficiency leads to an accumulation of GAGs in arteries, eyes, skeleton, joints, skin, ears and/or teeth. Glycosaminoglycans can also accumulate in the respiratory system, spleen, liver, central nervous system, bone marrow and blood (rarediseases.org). Depending on which of the eleven known enzymes are affected as well as the level of enzyme activity, different clinical manifestations are described varying from mild to severe forms with potentially early death. At present, MPSs are summarized in seven syndrome types (see Table 1 below) (orphanet 2018).