GCA and Alzheimer disease: Grancalcin (GCA) belongs to the penta‐EF‐hand Ca2+‐binding protein family,[9] which is implicated in the regulation of cell migration, apoptosis, and mobilization of immune cells.[10] We have previously reported that senescent GCA+ immune cells secrete plentiful GCA to repress osteogenesis, while Gca deletion in myeloid cells ameliorates skeletal aging.[11] As AD is also an aging‐related disease, it is interesting to speculate that GCA+ immune cells may also play a vital role in AD progression.