PSAP and frontotemporal dementia: One of the indicators of PGRN involvement in endolysosomal homeostasis is the detection of CLN11 hallmarks (i.e., accumulation of lipofuscin, saposin D, cathepsin D, lysosomal transmembrane protein 106B [TMEM106B], and LAMP1/2) in the brains, skin, and retinas of FTD-GRN patients [36, 37].