Also expressed by platelets in the periphery, the chemokine platelet factor 4 (PF4) (Jian et al., 2017) has exhibited differences in blood levels in AD when compared to controls (Yang et al., 2023), and similarly for MS (Cananzi et al., 1987) and PD (Shen et al., 2020). Here, PF4 is linked to myeloid sarcoma.