The presence of reduced NGFR/p75NTR ECD levels in CFS and in the brains of AD patients, which has a protective effect in AD-like pathology since it prevents the binding of Aβ NGFR/p75NTR, not only pushes to consider it as an AD powerful biomarker but opens new avenues for understanding why impaired NGFR/p75NTR signaling occurs in this disease. This evidence concerns the gene NGFR and Alzheimer disease.