The sequence variant c.1136C>T in exon 9 changes proline in position 379 to leucine (p.Pro379Leu). Studies in transfected cells show that p.Leu379 has retained some activity, is processed correctly and localized to the lysosomes. p.Pro379 is located near the active site area, and 3d-modelling indicates that p.Pro379Leu may destabilize the active site.