Krabbe disease, also called globoid-cell leukodystrophy, is caused by a deficiency of the lysosomal enzyme β-galactosylceramidase (GALC), resulting from pathogenic variants in both copies of the GALC gene. The GALC deficiency leads to increased levels of the primary galactosphingolipid substrates, galactosylceramide (GalCer) and psychosine (galactosylsphingosine, PSY), in the nervous system.