GBA1 and lysosomal storage disease: Gaucher disease (GD), the most common lysosomal storage disorder, is caused by recessive mutations in the glucocerebrosidase gene (GBA), which reduce activity of the enzyme beta-glucocerebrosidase (GCase).1 GD can be classified as non-neuronopathic (Type I) or neuronopathic (Type II and Type III).