Genome-wide association studies (GWAS) have identified possible genetic risk factors for AD preferentially expressed in microglia, such as CD33, Inositol Polyphosphate-5-Phosphatase D (INPP5D), CR1, Granulin Precursor (GRN) and ATP Binding Cassette Subfamily A Member 7 (ABCA7) [81]. This evidence concerns the gene CD33 and Alzheimer disease.