Chronic Lymphoproliferative Disorder of Natural Killer Cells: A Rare Event.

Chronic lymphoproliferative disorders are a diverse group of diseases derived from thymus lymphocytes (T cells), bursa of Fabricius cells (B cells), or natural killer (NK) cells. The diagnosis of chronic lymphoproliferative disorders of NK cells (CLPD-NK) is confirmed using antibody panels that are able to detect various stages of maturation of malignant cells. Autoimmune diseases and viral infections are often associated with an increase in circulating NK cells. It is hypothesized that certain viruses trigger the activation of NK cells which leads to the formation of NK cell clones. Majority of the cases are asymptomatic. However, some patients have systemic symptoms and cytopenias. Here, we report a case of CLPD-NK. Our patient's history and marked lymphocytosis on peripheral film raised the suspicion of a hematolymphoid malignancy for which flow cytometric analysis was done using an extensive panel which confirmed the diagnosis of CLPD-NK.