C3AR1 and Alzheimer disease: Although the C3AR1, CCR1, CCR5, and FCER1G genes have not been reported in relation to ALS, they have been linked to AD (Liu et al., 2014; Litvinchuk et al., 2018; Sierksma et al., 2020; Wojta et al., 2020), implying a role in neurodegeneration.