GALC and Krabbe disease: More than 110 mutations have been identified that effect GALC mRNA processing or cause deletions, frameshifts and missense mutations.12–20 The most common mutation is a 30 kb deletion resulting in complete absence of functional protein.16,21 Other forms of Krabbe disease are caused by protein truncation, catalytic inactivity, misfolding, mistargeting and premature degradation.22 Loss of GALC function causes accumulation of the cytotoxic metabolite psychosine, leading to cell death and widespread demyelination throughout the central and peripheral nervous systems.