There are other studies that have confirmed an association between the TREM-2 R47H mutation and the risk of Alzheimer’s disease [169,170]; it is noteworthy that a recent study suggested the possibility that an APOE4 allele in R47H mutation carriers may be essential for Alzheimer’s disease to be developed in these individuals [171]. This evidence concerns the gene APOE and early-onset autosomal dominant Alzheimer disease.