APP and Alzheimer disease: Since lysosomal dysfunction causes robust secretion of APP-CTFs and BMP, measuring those molecules in bodily fluids (e.g., plasma or CSF) of patients and preclinical models for disorders associated with lysosomal dysfunction, including AD, PD, ALS, FTD and obviously LSDs, may be informative, and may also provide novel opportunities in clinical settings for identification of pharmacodynamic biomarkers in relation to treatments that improve or correct lysosomal dysfunction.