The sequence variant c.1358C>T in exon 11 changes serine in position 453 with phenylalanine (p.Ser453Phe). Studies in transfected cells show that p.Phe453 has retained some activity, is processed correctly and localized to the lysosomes. p.Ser453 is located in the active site area, and 3d-modelling indicates that p.Ser453Phe may destabilize the active site.