KLRK1 and Crouzon syndrome-acanthosis nigricans syndrome: Our results demonstrated that the expression of activating receptors NKG2D and NKp44 in the total NK cell population and their two subsets decreased in the CA group compared to the CAN group (Fig. 5b, Additional file 1: Figure S4A–E), but no differences were observed in the expression of the other NKRs.