Next-generation sequencing, covering approximately 5,000 genes, including those associated with familial HLH, and wide range of IEI and complement deficiencies (such as C3, CFB, CFH, CFHR1, CFHR3, CFHR5, CFI) and MLPA analysis for CFHR1/CFHR3 deletions, was performed. This evidence concerns the gene CFHR1 and complement deficiency.