The first case-control study investigating the association between KIR genes and CN found that KIR2DL1, KIR2DL2, KIR2DL3, KIR2DL4, KIR3DL1, KIR3DL2, KIR2DL3, and KIR2DS4 are associated with an increased CN risk, while the KIR2DL5 is protective [157]. The gene discussed is KIR2DS4; the disease is cyclic hematopoiesis.