Pawlak-Adamska et al. in a population-based case-control study with 203 MS patients investigated and selected four PD-1 single-nucleotide polymorphisms: rs36084323 (PD-1.1), rs11568821 (PD-1.3), rs2227981 (PD-1.5), and rs2227982 (PD-1.9). Here, PDCD1 is linked to myeloid sarcoma.