FAS and hereditary hemophagocytic lymphohistiocytosis: In a Dutch cohort, NGS-based assessment for IEIs showed the highest yields among pediatric patients, within the immune dysregulation cluster, most patients received a diagnosis of familial hemophagocytic lymphohistiocytosis (HLH), with additional cases including autoimmune lymphoproliferative syndrome (ALPS), primarily attributed to pathogenic FAS variants [14].