Here, we confirm that PB CTPC from MM and MGUS patients are immunophenotypically more immature than their BM counterpart, as reflected by the expression of significantly lower levels of (i) markers that are typically acquired by PC during migration from secondary lymphoid tissues to the BM, such as CD38 and CD13860–64, and (ii) adhesion molecules that anchor PC to stromal structures such as CD56, CD81, and CD11760,65–67. Here, CD38 is linked to Miyoshi myopathy.