In the present study, all MPS IIIA patients had heparan-N-sulphatase (sulphamidase) (SGSH) enzyme deficiency and the range of enzyme activities in the affected patients was (0.2 to 1.0 nmol/mg prot/hr) with mean range of 0.29 ± 0.2 nmol/mg prot/17 h (Table 1). This evidence concerns the gene SGSH and mucopolysaccharidosis type 3A.