Herein we analyzed during MM progression: (i) the distribution of distinct NK cell subsets (i.e., CD56highCD16+/−, CD56lowCD16low and CD56lowCD16high) in the BM and PB from MM patients at different disease states and the expression levels of NKG2D, DNAM-1 and NKp30 on these populations; (ii) the functional capability of these distinct NK cell subsets to recognize and kill MM cells and their activity in the course of MM progression; (iii) the distribution and the functionality of these three subsets after autologous HSCT. The gene discussed is KLRK1; the disease is Miyoshi myopathy.