GALC encodes galactosylceramidase, a lysosomal enzyme that hydrolyzes galactose ester bonds of glycolipids, particularly galactosylceramide and galactosylsphingosine 12. This enzyme has very low activity under normal conditions and is responsible for the lysosomal catabolism of galactosylceramide, a major lipid component of myelin, kidney, and epithelial cells of the small intestine and colon 12. GALC deficiency causes Krabbe disease, a rare autosomal recessive leukodystrophy characterized by white matter degeneration 3. The disease manifests as infantile symptoms including irritability, progressive stiffness, developmental delay, and often death, with hematopoietic stem cell transplantation being the only potential treatment 3. Newborn screening programs measure GALC enzyme activity to identify affected individuals, with positive predictive values around 1.4% and an incidence of approximately 1 in 394,000 for infantile forms 3. Recent research suggests that common GALC variants may also influence Parkinson's disease risk through altered galactosylceramidase activity levels 4. The enzyme plays a crucial role in glycosphingolipid metabolism and lysosomal function, with mutations causing severe neurological pathology through disrupted myelin maintenance 5.