Introduction Varicella is a common childhood infection and can be complicated by secondary bacterial infection, pneumonia, acute cerebellar ataxia, meningoencephalitis, Reye’s syndrome, purpura fulminans and hemophagocytic syndrome, especially in immunocompromised hosts . After the host is infected by varicella zoster virus (VZV) via droplets, VZV completes 10 to 21 days of an incubation period in respiratory mucosa and reaches the lymph nodes and reticuloendothelial system after primary viremia. One of the primary defensive systems of the host against VZV is maintained by natural killer (NK cells, as a part of innate immunity . NK cells are involved in direct killing of virally infected cells via apoptosis with perforin-granzyme or FasFas ligand pathways. If there is a defect in NK cells count or function, defense against some viral infections will be impaired and complications will appear . Since varicella vaccination is not routinely applied in Turkey, epidemics can be observed in the wintertime and some children develop complications.