TREM2 and early-onset autosomal dominant Alzheimer disease: An increasing number of studies have shown that TREM-2 is involved in the progression of inflammatory diseases such as pulmonary inflammatory diseases, liver inflammatory diseases, periodontitis, inflammatory bowel disease, sepsis, Alzheimer’s disease, and other inflammatory-related diseases, playing a pivotal role in weakening or aggravating the development of the disease (12, 13, 18, 23).