OBJECTIVETo identify the characteristics of chronic natural killer cell lymphocytosis (CNKL).

METHODSThe clinical data of eight cases defined by the World Health Organization classification was retrospectively analyzed and related literatures were reviewed.

RESULTSHalf of the 8 patients were asymptomatic. Among them, the most common abnormalities were leukocytosis with the median of 11.8(4.5-20.0)×10⁹/L and high proportion of lymphocytes [0.78(0.51-0.89)], while anemia and thrombocytopenia only in 1 patient respectively. The absolute CD3⁻CD16⁺ NK cell count with the median of 5.7(2.4-9.6)×10⁹/L increased in peripheral blood. By the end of follow-up, except one case was lost, the other seven patients were in stable condition,including four cases without any medications and three patients receiving chlorambucil or glucocorticoid.

CONCLUSIONAs an indolent chronic lymphoproliferative disease, CNKL was presented with mild clinical symptoms and increased number of CD3⁻CD16⁺ NK cells in peripheral blood. Patients with symptoms could be treated with immunosuppressive therapy while those asymptomatic could be followed up without intervention.