The sequence variant c.598C>A in exon 4 changes histidine in position 200 to asparagine (p.His200Asn). Studies in transfected cells show that p.Asn200 is processed correctly, localized to the lysosomes and has retained some activity in one cell-type, but is inactive in another cell-type. p.His200 is located in the active site area, and 3d-modelling indicates that the substitution changes the stability of the active site.