Mucopolysaccharidosis type VII (MPS VII, Sly syndrome, beta-glucuronidase deficiency; MIM:253220) is an autosomal recessive lysosomal storage disease characterized by a deficiency of the enzyme beta-glucuronidase (GUSB; MIM:611499) which would normally cleave glucuronide residues from dematan sulphate, keratan sulphate and chondroitin sulphate, resulting in build up of these GAGs in cells and tissues (Sly et al. 1973). The gene encoding GUSB is 21 kb long, contains 12 exons and gives rise to two different types of cDNAs, through an alternate splicing mechanism (Miller et al. 1990). It maps to 7q11.21-q11.22 (Speleman et al. 1996). The phenotype is highly variable, ranging from severe causing death, non-immune hydrops fetalis (Vervoort et al. 1996) to mild forms with survival into adulthood (Storch et al. 2003). Most patients with the intermediate phenotype show hepatomegaly, skeletal anomalies, coarse facies, and variable degrees of mental impairment (Shipley et al. 1993, Tomatsu et al. 2009).