CTSS and amyotrophic lateral sclerosis: Although ALS represents a neurodegenerative disorder that predominantly affects the motor system, cognitive decline and behavioral symptoms occur in ALS patients (Phukan et al., 2007), and mutations in Macrophage colony-stimulation factor 1 receptor (Csf1r), a gene that interacts with both Ctss and Fcer1g, causes axonal spheroids as a sign of Wallerian degeneration (Lynch et al., 2016).