CD226 and pachyonychia congenita: Compared to the healthy controls, significantly decreased levels of activating receptors NKG2D, NKp30, NKp46, and DNAM-1 positive NK cells were observed in PC patients (P < 0.001, P < 0.001, P < 0.001, and P < 0.01, respectively); however, an significantly increased level of inhibitory receptor KIR3DL1 positive NK cells was observed in patients with PC (P < 0.001).