GRN and amyotrophic lateral sclerosis: Interestingly, a correlation between specific LRRK2 variants and plasma progranulin levels was highlighted by Caesar et al. [32], suggesting that LRRK2 mutations could be implicated in the ALS-FTD spectrum, also based on their role in altering one or more specific pathways, including autophagy, immune response, neurite outgrowth, and vesicle trafficking [33].