GBA1 and lysosomal storage disease: Biallelic (homozygous or compound heterozygous) mutations in the GBA1 gene, encoding the lysosomal enzyme glucocerebrosidase (GCase; EC 3.2.1.45), are pathognomonic for the commonest lysosomal storage disorder (LSD) Gaucher disease (GD) (Grabowski 2008).