Pedigree Gene Investigation and Parameters of NK Cell Activity, CD107a Degranulation Amd HLH Related Defective Protein Play Significant Role in the Diagnosis of Primary HLH

Abstract This study aims to evaluate the significance of pedigree genetic screening and rapid immunological parameters in the diagnosis of primary HLH and explore their correlation. Twelve Chinese families of primary HLH with mutations in PRF1, UNC13D, LYST, RAB27A, SH2D1A, BIRC4 were recruited and conducted pedigree investigation, including family genetic screening, NK cell activity, CD107a degranulation and expression of HLH related defective protein. Ten patients were identified with homozygous, compound heterozygous, or hemizygous mutations in PRF1, UNC13D, RAB27A, SH2D1A and BIRC4, including one case of homozygous mutation (c.1349C>T:p.T450M) and four cases of compound heterozygous mutations (frameshift deletion c.65delC:p.P22fs and c.G503A:p.S168N; c.1168C>Tp.R390X and c.1349C>T:p.T450M; frameshift mutation c.1090_1091delCT:p.T364fsX93 and c.1349C>T:p.T450M; non-frameshift deletions c.1083_1094del:p.361_365del and c.T172C :p.S58P) in PRF1, one case of homozygous mutation (c.G2588A:p.G863D) and one compound heterozygous (c.C640T:p.R214X and c.G407A:p.C136Y) in UNC13D, one case of homozygous mutation (c.C244T:p.R82C) in RAB27A, and two male cases of hemizygous mutations in SH2D1A(c.32T>G:p.I11S) and BIRC4(c.G592A:p.V198M). Meanwhile, two patients were identified mutations in two or three different gene, including a male with a hemizygous mutation in SH2D1A(c.7G>T:p.A3S) and a heterozygous mutation(c.127C>A: p.L43M) in PRF1, and a female with three hemizygous mutations respectively in UNC13D(c.G680A:p.R227H), LYST(c.A8368C:p.K2790Q) and BIRC4(c.C962G:p.A321G).The primary HLH patients and their family members presented different levels of decreased NK cell activity. Individuals who were found mutations in PRF1, SH2D1A and BIRC4 showed low expression of perforin, SAP and XIAP. And the patients with homozygous and compound heterozygous mutations in UNC13D and RAB27A showed significant reducing of cytotoxic degranulation function and their family members presented normal or different levels of decreased CD107a. The patient with combination defects involving two genes(UNC13D and LYST) in the degranulation pathway showed decreased of CD107a degranulation which implied a digenic inheritance and diagnosed primary HLH. Pedigree genetic screening and rapid detection of immunological parameters play an important role in the diagnosis of primary HLH and demonstrate good consistency.