CTSD and Niemann-Pick disease, type C1: Increased serum levels of galectin-3 (LGALS3), a pro-inflammatory molecule, and cathepsin D (CTSD), a lysosomal aspartic protease, as well as various cholesterol oxidation products have been found to be potential serum biomarkers in murine models that may aid in diagnosis and therapeutic monitoring in NPC1 patients [6,7].