Hemophagocytic syndrome (HPS, additionally known as hemophagocytic lymphohistiocytosis) is a disorder characterized by an aberrant lytic response of natural killer cells (NKs) and cytotoxic CD8+ T lymphocytes (CTLs) (1–4), leading to an overactive yet less efficient immune reaction to an antigenic response. Here, CD8A is linked to hemophagocytic syndrome.