A pan European study found 97% of FHL3-5 and 85% of GS2 and CHS cases had abnormal percentage of NK cell degranulation (<5% CD107a+ NK cells) to give an overall sensitivity of 96% and specificity of 88% in diagnosing a genetic degranulation disorder (Table 1) (21). This evidence concerns the gene LAMP1 and Chédiak-Higashi syndrome.