PRF1 and Chédiak-Higashi syndrome: These include familial HLH caused by autosomal recessive mutations in Perforin (PRF1), MUNC 13-4 (UNC13D), MUNC 19-2 (STXBP2), syntaxin 11 (STX11) as well as other IEIs such as Type II Hermansky-Pudlak syndrome (AP3B1), Chediak-Higashi syndrome (LYST) and Griscelli syndrome (RAB27A) (Hayden et al., 2016).