The mucopolysaccharidoses (MPS) are a group of rare, inherited lysosomal storage disorders caused by deficiencies of enzymes catalyzing the stepwise degradation of glycosaminoglycans (GAGs, originally called mucopolysaccharides) (Neufeld & Muenzer in Scriver et al. 2001). Catabolism of the GAGs dermatan sulfate, heparan sulfate, heparin, keratan sulfate, chondroitin sulfate or hyaluronan may be blocked at one or more steps, resulting in lysosomal accumulation of GAG fragments of varying size. Over time these collect in the cells, blood and connective tissues ultimately resulting in progressive irreversible cellular damage which affects appearance, physical abilities, organ and system function, vision, and usually mental development (Lehman et al. 2011, Ashworth et al. 2006). Life expectancy is also reduced. There are 11 known enzyme deficiencies that give rise to 7 distinct MPS. These disorders are biochemically characterized by elevated levels of partially or undegraded GAGs in lysosomes, blood, urine and cerebro-spinal fluid (Muenzer 2011, Coutinho et al. 2012). The MPS are part of the lysosomal storage disease family, a group of about 50 genetic disorders caused by deficient lysosomal proteins (Ballabio & Gieselmann 2009).