PTPRC and Miyoshi myopathy: CD45 is predominantly expressed by less mature plasma cells and its expression has been reported to be associated with worse outcome in MM.34 Moreover, the prevalence of Heca452-positive cells in the CD45-positive fraction may be favored under the hypoxic environment of the BM, which, at least in mice, seems to be advantageous for the CD45-positive MM cells.46 Finally, samples from RRMM patients showed a significantly higher percentage of Heca452-positive cells in the PB compared to those from NDMM patients.