In primary HLH, uncontrolled immune activation is the result of gene defects affecting perforin‐dependent cytotoxicity of NK and CD8 T cells (Schmid et al, 2010; Janka & Lehmberg, 2014; de Saint Basile et al, 2015; Chinn et al, 2018). Here, CD8A is linked to hemophagocytic syndrome.