Gaucher disease is a prototypical lysosomal sphingolipid storage disorder caused by pathogenic variants in GBA1, resulting in glucocerebrosidase deficiency and accumulation of bioactive lipids, including glucosylceramide and glucosylsphingosine (lyso-Gb1). While non-neuronopathic Gaucher disease is effectively managed with enzyme replacement and substrate reduction therapies, neuronopathic forms remain largely refractory to treatment due to progressive central nervous system (CNS) involvement and limited penetration of current therapies across the blood–brain barrier. Disease pathobiology extends beyond lysosomal substrate accumulation to encompass dysregulated sphingolipid signaling, particularly sphingosine-1-phosphate (S1P)-mediated “inside-out” signaling, alongside neuroinflammation, oxidative stress, and glial activation, which collectively drive neurodegeneration. In this review, we synthesize current knowledge on sphingolipid metabolism and signaling in neuronopathic Gaucher disease and integrate these mechanisms into a three-tier, CNS-focused biomarker framework. The first tier comprises substrate-proximal markers of lysosomal burden (lyso-Gb1), which reflect GCase deficiency and correlate with systemic disease severity but incompletely capture CNS pathology. The second tier comprises markers of glial activation and neuroinflammation (glial fibrillary acidic protein GFAP, glycoprotein non-metastatic melanoma protein B GPNMB), which reflect the downstream neuroimmune response to sphingolipid accumulation. The third tier comprises markers of neuroaxonal injury (neurofilament light chain NfL), which index irreversible neuronal damage as the terminal consequence of uncontrolled CNS disease. Together, these tiers map distinct but mechanistically interconnected stages of disease progression, from lysosomal dysfunction through glial activation to neuroaxonal loss, enabling stage-specific interpretation of biomarker signals that single-analyte approaches cannot provide. We further examine how S1P-mediated inside-out signaling links intracellular lipid dysregulation to extracellular neuroimmune and neurovascular responses and how the blood–brain barrier shapes compartment-dependent biomarker behavior across cerebrospinal fluid and blood. By grounding biomarker selection in this mechanistic cascade, the framework provides explicit criteria for pairing analytes across tiers, interpreting discordance between peripheral and CNS compartments, and designing multi-modal endpoints for clinical trials of CNS-penetrant therapies. Despite these advances, significant challenges remain, including limited longitudinal datasets, variability in assay methodologies, and incomplete validation of biomarkers as surrogates of CNS disease progression. Addressing these gaps will require harmonized, multi-modal approaches integrating biochemical, functional, and imaging measures. By positioning neuronopathic Gaucher disease as a model of sphingolipid-driven neurodegeneration, this review highlights opportunities for biomarker-guided therapeutic development relevant to Gaucher disease and the broader spectrum of sphingolipid-associated neurological disorders.
Casazza et al. (Tue,) studied this question.