Galactosylsphingosine is a galactoside of sphingosine and a constituent of cerebrosides. The lysosomal enzyme β-galactosylceramidase is responsible for cleaving the glycosydic linkage of galactosylceramide and galactosylsphingosine. Accumulation of galactosylsphingosine during β-galactosylceramidase deficiency, as seen with Krabbe disease, is cytotoxic and preferentially affects oligodendrocytes, leading to progressive demyelination and infiltration of activated macrophages into the brain.