GALC and lysosomal storage disease: Krabbe disease belongs to the group of lysosomal storage disorders and is caused by mutations in the GALC gene, leading to a deficiency of the lysosomal hydrolase galactocerebrosidase (GALC) and subsequently, to an accumulation of psychosine—a cytotoxic metabolite that induces apoptosis in oligodendrocytes and Schwann cells.