By definition, CHIP does not significantly affect blood cell counts but can progress to do so, with the terms clonal cytopenia of undetermined significance (CCUS) (11, 19) and clonal monocytosis of undetermined significance (CMUS) (20) used to describe cytopenia(s) or monocytosis, respectively, in the presence of a CH mutation, in individuals without overt neoplasia, such as a myelodysplastic syndrome (MDS) or chronic myelomonocytic leukemia (CMML). This evidence concerns the gene C4B and myelodysplastic syndrome.