IRAK4 and hereditary hemophagocytic lymphohistiocytosis: The steep early decline in survival we observed in patients with disorders of immune regulation and innate IEI may argue for an extension of NBS to other immediately life-threatening IEI (e.g., familial hemophagocytic lymphohistiocytosis [FHL], XLP1, MyD88/IRAK4 deficiencies, and IPEX syndromes).