PRF1 and hereditary hemophagocytic lymphohistiocytosis: Specifically, most patients clustered within the immune dysregulation category were diagnosed with familial hemophagocytic lymphohistiocytosis (FHL) type 2 (n=3/10;30%), type 3 (n=2/10; 20%) and type 4 (n=1/10; 10%), based on homozygotic pathogenic variants in PRF1, UNC13D, and STX11, respectively (Table S3).