KLRD1 and Miyoshi myopathy: Functional studies suggest that, although NK-cells remain functional in MGUS patients, they may display functional changes in MM and lose cytotoxicity particularly in advanced MM.15, 19, 29, 30 NK-cell function is often reflected in changes in the NK-cell receptor repertoire, which includes the natural cytotoxicity receptors (NCRs) and NKG2D.