PARP1 and myeloid sarcoma: Using postmortem brain of MS patients, previous study reported that PAR (the product of PARP1 enzymatic activity) was located primarily in OLs and as well as macrophages/microglia and astrocytes in MS demyelination plaques.[15] The density of PAR+ cells was found in higher density in pattern III plaques (i.e., primary oligodendrogliopathy) than pattern II plaques and positively correlated with the density of cells positive for nuclear AIF, a unique hallmark of PARP1‐mediated cell death.[15] This clinical observation provides the rationale for studying the role of PARP1 in demyelination.