The sequence variant c.2671G>A in exon 22 changes glycine in position 891 to arginine (p.Gly891Arg). Studies in transfected cells show that p.Arg892 is inactive, not processed and retained in the ER. p.Gly891 is located in a hinge and 3d-modelling indicates that p.Gly891Arg causes misfolding of the enzyme.