Clinical Presentations, Diagnosis, and Genetic Features of Hemophagocytic Lymphohistiocytosis: A Single Institutional Experience With the Saudi Population.

Background Hemophagocytic lymphohistiocytosis (HLH) is an uncommon, potentially fatal condition caused by high immune activation. The present study aimed to identify the clinical manifestations, geographic distribution, and associated pathogenic genetic mutations of HLH in Saudi Arabia. Method A retrospective cross-sectional study was conducted at King Fahad Medical City (KFMC), with a total of 59 patients diagnosed with HLH in the period between 2006 and 2018. All genetic results and clinical and biochemical data were retrieved and statistically analyzed using IBM SPSS Statistics for Windows, Version 25 (Released 2017; IBM Corp., Armonk, New York, United States). Results The results revealed that 48 patients (81.4%) had 15 pathogenic mutations of primary HLH whereas 8 (13.6%) patients had no genetic mutation. The most common variant mutation identified was c.1430C>T of the STXBP2 gene (42.4% of total patients), followed by c.1122G>A of the PRF1 gene (10.2% of patients), which demonstrated a distinctive geographic and tribal association. Patients with RAB27A mutation tend to present at an older age than the others with a median age of presentation of 5.5 months vs 2 months for patients with PRF1 mutations. No significant differences in clinical features were observed among the various groups. Conclusion This study highlights the incidence of genetic mutations among the Saudi population with HLH. The STXBP2 is the most common mutation followed by PRF1 mutations, many mutation variants are associated with a distinctive tribal and geographic association.

Overcoming Diagnostic Challenges: A Rare Presentation of Primary Hemophagocytic Lymphohistiocytosis (HLH) in a Young Female and the Importance of Timely Recognition.

Hemophagocytic lymphohistiocytosis (HLH) is a severe life-threatening hematological disorder characterized by the dysregulation of the immune system and a hyperinflammatory response. Prompt treatment is crucial to prevent fatality. Although primarily affecting infants, HLH can also occur in children and adults. It is classified as primary and secondary, with primary HLH being genetic and predominantly affecting children. Secondary HLH is triggered by infections, malignancy, metabolic disorders, and rheumatological conditions. Diagnosis is based on the HLH-2004 criteria, considering clinical and laboratory parameters. Early diagnosis and treatment improve prognosis. Treatment follows the HLH-94 and HLH-2004 protocol and consists of eight weeks of induction therapy with cyclosporine, corticosteroids, and etoposide. This case describes a 26-year-old female diagnosed with HLH and successfully treated according to the protocol. The patient exhibited improvement and was discharged, demonstrating the importance of early diagnosis and appropriate management in adult HLH cases.

Immune Rejection Mediated by prf1 and gzmb Affects the Colonization of Fat Greenling (Hexagrammos otakii) Spermatogonia in Heterotransplantation.

Fish germ cell transplantation holds great potential for conserving endangered species, improving cultured fish breeds, and exploring reproductive techniques. However, low transplantation efficiency is a common issue in heterotransplantation. This study transplanted fat greenling (Hexagrammos otakii) spermatogonia into the testes of spotted sea bass (Lateolabrax maculatus) to investigate factors that might affect the colonization and fixation of heterologous transplanted germ cells. Results indicated that transplanted fat greenling spermatogonia cells were successfully detected in the early transplantation phase in spotted sea bass. Their numbers gradually decreased over time, and after 10 days post-transplantation, more than 90% of the transplanted cells underwent apoptosis. Transcriptome sequencing analysis of the testes of spotted sea bass and fat greenling spermatogonia on days 1 and 10 post-transplantation revealed that this apoptosis process involved many immune-related genes and their associated signaling pathways. Acute immune rejection marker genes prf1 and gzmb were detected in the spotted sea bass testes, while immune tolerance genes lck and zap-70 were expressed in the fat greenling spermatogonia. Additionally, differential expression of prf1 and gzmb genes was screened from spotted sea bass, with experimental evidence indicating that PRF1 and GZMB protein from spotted sea bass primarily induce apoptosis in transplanted fat greenling spermatogonia via the mitochondrial apoptosis pathway, at the protein level. This suggests that the difficulties in heterotransplantation are primarily related to acute immune rejection, with PRF1 and GZMB playing significant roles.

Hemophagocytic Lymphohistiocytosis Gene Variants in Severe Aplastic Anemia and Their Impact on Hematopoietic Cell Transplantation Outcomes.

Germline genetic testing for patients with severe aplastic anemia (SAA) is recommended to guide treatment, including the use of immunosuppressive therapy and/or adjustment of hematopoietic cell transplantation (HCT) modalities. Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory condition often associated with cytopenias with autosomal recessive (AR) or X-linked recessive (XLR) inheritance. HLH is part of the SAA differential diagnosis, and genetic testing may identify variants in HLH genes in patients with SAA. The impact of pathogenic/likely pathogenic (P/LP) variants in HLH genes on HCT outcomes in SAA is unclear. In this study, we aimed to determine the frequency of HLH gene variants in a large cohort of patients with acquired SAA and to evaluate their association(s) with HCT outcomes. The Transplant Outcomes in Aplastic Anemia project, a collaboration between the National Cancer Institute and the Center for International Blood and Marrow Transplant Research, collected genomic and clinical data from 824 patients who underwent HCT for SAA between 1989 and 2015. We excluded 140 patients with inherited bone marrow failure syndromes and used exome sequencing data from the remaining 684 patients with acquired SAA to identify P/LP variants in 14 HLH-associated genes (11 AR, 3 XLR) curated using American College of Medical Genetics and Genomics/Association of Molecular Pathology (ACMG/AMP) criteria. Deleterious variants of uncertain significance (del-VUS) were defined as those not meeting the ACMG/AMP P/LP criteria but with damaging predictions in ≥3 of 5 meta-predictors (BayesDel, REVEL, CADD, MetaSVM, and/or EIGEN). The Kaplan-Meier estimator was used to calculate the probability of overall survival (OS) after HCT, and the cumulative incidence calculator was used for other HCT outcomes, accounting for relevant competing risks. There were 46 HLH variants in 49 of the 684 patients (7.2%). Seventeen variants in 19 patients (2.8%) were P/LP; 8 of these were loss-of-function variants. Among the 19 patients with P/LP HLH variants, 16 (84%) had monoallelic variants in genes with AR inheritance, and 3 had variants in XLR genes. PRF1 was the most frequently affected gene (in 8 of the 19 patients). We found no statistically significant differences in transplantation-related factors between patients with and those without P/LP HLH variants. The 5-year survival probability was 89% (95% confidence interval [CI], 72% to 99%) in patients with P/LP HLH variants and 70% (95% CI, 53% to 85%) in those with del-VUS HLH variants, compared to 66% (95% CI, 62% to 70%) in those without variants (P = .16, log-rank test). The median time to neutrophil engraftment was 16 days for patients with P/LP HLH variants and 18 days in those with del-VUS HLH variants or without variants combined (P = .01, Gray's test). No statistically significant associations between P/LP HLH variants and the risk of acute or chronic graft-versus-host disease were noted. In this large cohort of patients with acquired SAA, we found that 2.8% of patients harbored a P/LP variant in an HLH gene. No negative effects of HLH gene variants on post-HCT survival were noted. The small number of patients with P/LP HLH variants limits the study's ability to provide conclusive evidence; nonetheless, our data suggest that there is no need for special transplantation considerations for patients with SAA carrying P/LP variants.

Familial Hemophagocytic Lymphohistiocytosis (FHLH) Perforin Deficiency: A Case Study and Literature Review.

Hemophagocytic lymphohistocytosis (HLH) is a severe and fatal immunological disorder that is either primary (i.e., familial) or secondary (i.e., acquired). The primary type comprises autosomal recessive disorders with gene mutations related to natural killer cells and cytotoxic T-cells, whereas the secondary type is related to other pathological causes, such as Epstein-Barr virus, bacterial or fungal infection, autoimmune conditions or autoinflammatory diseases, metabolic disorders, and cancer. In this report, we discuss a 37-day-old male who was brought to the emergency room with fever, decreased activity, and hepatosplenomegaly, with a strong family history of unknown cause of death for three siblings who died at the ages of one to two months. A whole exome sequencing confirmed the clinical diagnosis of familial HLH due to mutation in the PRF1 gene. We note the special importance of genetic counselling and antenatal screening or early neonatal screening in families affected by HLH, as this case highlights the importance of early diagnosis and intervention of primary HLH.

Late Onset of Primary Hemophagocytic Lymphohistiocytosis (HLH) with a Novel Constellation of Compound Heterozygosity Involving Two Missense Variants in the PRF1 Gene.

Hemophagocytic lymphohistiocytosis (HLH) is a rare but in most cases life-threatening immune-mediated disease of the hematopoietic system frequently associated with hematologic neoplasms. Here, we report on a case in which we detected a novel constellation of two missense variants affecting the PRF1 gene, leading to de novo primary HLH. Diagnostics included a comprehensive clinical work-up and standard methods of hematopathology as well as extended molecular genomics based on polymerase chain reaction (PCR) reactions and the calculation of three-dimensional molecule reconstructions of PRF1. Subsequently, a comprehensive review of the literature was performed, which showed that this compound heterozygosity has not been previously described. The patient was a 20-year-old female. Molecular diagnostics revealed two heterozygous missense variants in the PRF1 gene (A91V and R104C) on exon 2. Apart from the finding of two inconclusive genetic variants, all clinical criteria defined by the HLH study group of Histiocyte Society were met at initial presentation. The final diagnosis was made in cooperation with the Consortium of German HLH-reference centers. Here, chemotherapy did not lead to sufficient sustained disease control. Therefore, the decision for allogenic hematopoietic stem cell transplantation (alloHSCT) was made. Hitherto, the duration of response was 6 months. Due to severe and unmanageable hepatic graft-versus-host disease (GvHD), the patient died. We report on a novel constellation of a compound heterozygosity containing two missense variants on exon 2 of the PRF1 gene. To the authors' best knowledge, this is the first presentation of a primary HLH case harboring this genomic constellation with late-onset clinical manifestation.

Hemophagocytic lymphohistiocytosis with a hemizygous PRF1 c.674G>A mutation.

Hemophagocytic lymphohistiocytosis(HLH) is a rare highly-fatal disease presenting with fever, hepatosplenomegaly, and pancytopenia and has a poor prognosis. Homozygous or semi-zygous or complex heterozygous variants can cause familial HLH and heterozygous carriers are frequently seen in secondary HLH. A 42-year-old male patient was admitted to the hospital for persistent fever, fatigue, and splenomegaly. Investigations revealed hypertriglyceridemia, hyperlactatemia dehydrogenaseemia, hyperferritinemia, and elevated levels of soluble cluster of differentiation 25. We found a heterozygous mutation of PRF1: c.674G>A (p.R225Q) through next-generation sequencing technology of hemophagocytic-lymphohistiocytosis-related genes. After a brief remission with dexamethasone and etoposide-based therapy, the disease relapsed quickly, and an allogeneic hematopoietic stem cell transplant was performed to achieve complete remission. To date, the patient's condition was in complete remission. Our study detected a rare missense mutation in the PRF1 gene in a patient with HLH disease and the c.674G>A mutation may be rated as a possible pathogenic variant.

Brain MRI Findings of Hemophagocytic Lymphohistiocytosis With a Heterozygous PRF1 Gene Mutation Masquerading As CLIPPERS: A Case Report.

Familial hemophagocytic lymphohistiocytosis is a rare and potentially life-threatening genetic condition characterized by unsuppressed immune activation and hypercytokinemia. Chronic Lymphocytic Inflammation with Pontine Perivascular Enhancement Responsive to Steroids (CLIPPERS) is a central nervous system inflammatory disorder characterized by punctate and curvilinear gadolinium-enhancing lesions in the brainstem, cerebellum, and spinal cord, which responds well to corticosteroid treatment. Hemophagocytic lymphohistiocytosis has been known to mimic CLIPPERS on neuroimaging, and patients previously diagnosed with CLIPPERS may carry familial hemophagocytic lymphohistiocytosis-related gene mutations that serve as predisposing factors. In this article, we describe a case initially diagnosed with CLIPPERS based on characteristic magnetic resonance imaging features and clinical course, who was later diagnosed with hemophagocytic lymphohistiocytosis based on a heterozygous familial hemophagocytic lymphohistiocytosis-associated PRF1 gene mutation.

[Gene Polymorphisms of Patients with Lymphoma-Associated Hemophagocytic Syndrome in Longyan area, Fujian Province].

OBJECTIVE: To analyze the gene polymorphisms of patients with lymphoma-associated hemophagocytic syndrome in Longyan area, Fujian province. METHODS: A total of 125 patients with lymphoma-associated hemophagocytic syndrome in Longyan, Fujian province, admitted to Longyan First Hospital from May 2017 to November 2020 were selected. Peripheral venous blood was collected from all the patients, and the genotypes of perforin 1 (PRF1) and interleukin-10 (IL-10) gene loci were detected by PCR-fluorescence probe method, and the correlation between PRF1 and IL-10 gene polymorphisms and lymphoma-associated hemophagocytic syndrome was analyzed. RESULTS: The mutation frequencies of PRF1 gene loci rs885821 (C>T), rs885822 (C>T), rs1889490 (G>A) in patients with lymphoma-associated hemophagocytic syndrome were 10.40%, 78.8% and 64.4%, respectively. The mutation frequencies of rs1800872 (A>C), rs1800871 (C>T) and rs1800896 (G>A) of IL-10 loci were 56.0%, 45.2% and 77.6%, respectively. CONCLUSION: PRF1 and IL-10 gene loci were polymorphic in patients with lymphoma-associated hemophagocytic syndrome in Longyan area, Fujian province. Alleles C and G of PRF1 and IL-10 were risk factors, and alleles T and A were protective factors.

Familial CNS-Isolated Hemophagocytic Lymphohistiocytosis Due to a Novel PRF1 Mutation Triggered by SARS-CoV2.

Background: Hemophagocytic lymphohistiocytosis (HLH) is a potentially fatal hyperinflammatory condition that presents with fever, hepatosplenomegaly, and characteristic laboratory findings. Mutations in the perforin gene PRF1 have been implicated in cases of familial HLH (fHLH) and can cause isolated CNS-HLH in the absence of systemic HLH. Results: A five year-old boy presented with three weeks of headache, blurry vision, and emesis. He was diagnosed with acute disseminated encephalomyelitis (ADEM), thought to be triggered by SARS-CoV-2 given positive nasopharyngeal testing. He completed a five day course of high dose IV methylprednisolone and plasma exchange. In the subsequent months, he was admitted twice due to worsening clinical and radiological activity and after several courses of IV pulse steroids, plasmapheresis, and IV immunoglobulin (IVIG), his condition stabilized with rituximab and monthly IVIG. A few months later, his younger brother presented with a similar syndrome. It was discovered that his parents were second cousins, leading to concern for a genetic disorder. Genetic testing revealed a homozygous mutation for PRF1 in both siblings (variant c.4422G>A). Conclusions: This is the first presentation of CNS-isolated familial HLH triggered by SARS-CoV-2 in the pediatric population. Furthermore, this is the first report of this specific PRF1 mutation, the variant c.4422G>A, as pathogenic. It highlights the relevance of genetic testing in pediatric neuroinflammatory disorders that do not respond adequately to conventional treatments. It is possible that as our knowledge in neurogenetics develops, certain genes will be identified as predisposing factors to syndromes such as ADEM.

RF1 Gene Mutation in Familial Hemophagocytic Lymphohistiocytosis 2: A Family Report and Literature Review.

OBJECTIVE: Gene mutation analysis was performed on a family with familial hemophagocytic lymphohistiocytosis (FHL) so as to provide an accurate etiological diagnosis, leading to genetic counseling for the family members. METHODS: The clinical data of two probands (siblings) with FHL in one family were analyzed, and eight genes related to the onset of the primary hemophagocytic lymphohistiocytosis (pHLH) (PRF1, UNC13D, STX11, STXBP2, SH2D1A, BIRC4/XIAP, Rab27a, LYST) were detected and analyzed in the probands and their parents with whole exome sequencing. RESULTS: Proband 1 was a two-year-old male with the clinical manifestations of fever, hepatosplenomegaly, and a decreased peripheral blood cell count, sCD25: 12504pg/mL. The results of genetic testing showed that there was a c.1349C>T heterozygous missense mutation and a c.853_855del heterozygous mutation in the PRF1 in proband 1. Proband 2 was an eight-year-old female with the clinical manifestations of convulsions and disturbance of consciousness with fever. The genetic test results were the same as those of proband 1. There was a single heterozygous mutation in the parents of the probands, and both probands had compound heterozygous mutations. CONCLUSION: According to the clinical manifestations, laboratory tests, and results of the family molecular genetic testing, the probands could be clinically diagnosed as FHL2. The results of gene sequencing revealed that this was an autosomal recessive family with familial hemophagocytic syndrome. A rare pathogenic mutation (c.853_855del) in the PRF1 was discovered in the two patients with HLH.

Spectrum mutations of PRF1, UNC13D, STX11, and STXBP2 genes in Vietnamese patients with hemophagocytic lymphohistiocytosis.

INTRODUCTION: The prevalence of gene mutations in hemophagocytic lymphohistiocytosis (HLH) varied between studies. Thus far, data on the genetic background of HLH in Vietnamese patients are limited. METHODS: We recruited 94 HLH patients and analyzed for the 4 genes using Sanger sequencing technology. RESULTS: Pathogenic variants were observed in 36 (38.29%) patients, including 27 in UNC13D, 5 in STXBP2, 3 in PRF1, and 2 in STX11 (one patient with digenic variants in both UNC13D and STX11). Monoallelic variants accounted for 77.8% of all cases with mutation. A total of 23 different types of pathogenic variants were documented in the 4 genes tested, including 15 in UNC13D, 3 in PRF1, 3 in STXBP2, and 2 in STX11. Interestingly, the novel splicing variant c.3151G>A in UNC13D was recurrently identified in 8 unrelated patients. CONCLUSION: Vietnamese patients with HLH showed a distinct genetic variant spectrum, in which UNC13D is the predominant genetic lesion associated with HLH.

Mutational analysis of apoptotic genes in familial aggregation of hematological malignancies.

INTRODUCTION: Apoptosis deregulation have been associated to tumorigenesis process and was highlighted as a prominent hallmark of cancer. Several mutations have been reported in several forms of Blood cancer. However, it has never been investigated in familial aggregations of hematological malignancies. METHODS: In this study, we performed a mutational analysis by sequencing the entire coding regions in four key apoptotic genes FAS, FASLG, CASP8 and CASP10 in 92 independent families belonging to French and Tunisian populations and diagnosed with several forms of familial hematological malignancies. RESULTS: We report 15 genetic variations among which 7 were previously reported in several form of cancers and have a potential effect on gene expression. Particularly, the CASP8 variants p.Asp302His and p.Lys337Lys were detected in 15% and 10% of our group of patients respectively and were previously reported in association to breast cancer and to breast cancer susceptibility. DISCUSSION: In this study, we do not report the underlining deleterious mutations in familial hematological malignancies, but we describe some variants with potential risk of developing blood cancer. To gain further insights on the association between apoptosis pathway deregulation and familial hematological malignancies, more apoptotic genes should be investigated.

Genetic and clinical characteristics of pediatric patients with familial hemophagocytic lymphohistiocytosis.

BACKGROUND: Our study was designed to investigate the frequencies and distributions of familial hemophagocytic lymphohistiocytosis (FHL) associated genes in Saudi patients. METHODS: FHL associated gene screening was performed on 87 Saudi patients who were diagnosed with hemophagocytic lymphohistiocytosis (HLH) between 1995 and 2014. The clinical and biochemical profiles were also retrospectively captured and analyzed. RESULTS: Homozygous mutations and mono-allelic variants were identified in 66 (75.9%) and 3 (3.5%) of the study participants, respectively. STXBP2 was the most frequently mutated gene (36% of patients) and mutations in STXBP2 and STX11 accounted for 58% of all FHL cases and demonstrated a specific geographical pattern. Patients in the FHL group presented at a significantly younger age than those belonging to the unknown-genetics group (median, 3.9 vs. 9.4 mo; P=0.005). The presenting clinical features were similar among the various genetic groups and the 5-year overall survival (OS) was 55.4% with a 5.6 year median follow-up. Patients with PRF1 mutations had a significantly poorer 5-year OS (21.4%, P =0.008) and patients undergoing hematopoietic stem cell transplant (72.4%) had a significantly better 5-year OS (66.5% vs. 0%, P =0.001). CONCLUSION: Our study revealed the predominance of the STXBP2 mutations in Saudi patients with FHL. A genetic diagnosis was possible in 80% of the cohort and our data showed improved survival in FHL patients who underwent hematopoietic stem cell transplant.

NF-κB c-Rel Is Dispensable for the Development but Is Required for the Cytotoxic Function of NK Cells.

Natural Killer (NK) cells are cytotoxic lymphocytes critical to the innate immune system. We found that germline deficiency of NF-κB c-Rel results in a marked decrease in cytotoxic function of NK cells, both in vitro and in vivo, with no significant differences in the stages of NK cell development. We found that c-Rel binds to the promoters of perforin and granzyme B, two key proteins required for NK cytotoxicity, and controls their expression. We generated a NK cell specific c-Rel conditional knockout to study NK cell intrinsic role of c- Rel and found that both global and conditional c-Rel deficiency leads to decreased perforin and granzyme B expression and thereby cytotoxic function. We also confirmed the role of c-Rel in perforin and granzyme B expression in human NK cells. c-Rel reconstitution rescued perforin and granzyme B expressions in c-Rel deficient NK cells and restored their cytotoxic function. Our results show a previously unknown role of c-Rel in transcriptional regulation of perforin and granzyme B expressions and control of NK cell cytotoxic function.

Adult onset type 2 familial hemophagocytic lymphohistiocytosis with PRF1 c.65delC/c.163C>T compound heterozygous mutations: A case report.

BACKGROUND: Familial hemophagocytic lymphohistiocytosis (FHL) is a primary immunodefici-ency disease caused by gene defects. The onset of FHL in adolescents and adults may lead clinicians to ignore or even misdiagnose the disease. To the best of our knowledge, this is the first report to detail the clinical features of type 2 FHL (FHL2) with compound heterozygous perforin (PRF1) defects involving the c.163C>T mutation, in addition to correlation analysis and a literature review. CASE SUMMARY: We report a case of a 27-year-old male patient with FHL2, who was admitted with a persistent fever and pancytopenia. Through next-generation sequencing technology of hemophagocytic lymphohistiocytosis (HLH)-related genes, we found compound heterozygous mutations of PRF1: c.65delC (p.Pro22Argfs*29) (frameshift mutation, paternal) and c.163C>T (p.Arg55Cys) (missense mutation, maternal). Although he did not receive hematopoietic stem cell transplantation, the patient achieved complete remission after receiving HLH-2004 treatment protocol. To date, the patient has stopped taking drugs for 15 mo, is in a stable condition, and is under follow-up observation. CONCLUSION: The delayed onset of FHL2 may be related to the PRF1 mutation type, pathogenic variation pattern, triggering factors, and the temperature sensitivity of some PRF1 mutations. For individual, the detailed reason for the delay in the onset of FHL warrants further investigation.

PRF1 is a prognostic marker and correlated with immune infiltration in head and neck squamous cell carcinoma.

PURPOSE: Head and neck squamous cell carcinoma (HNSCC) is a highly invasive malignancy with poor survival. Perforin (PRF1) plays essential roles in host immunity. Our research intended to identify the correlations of PRF1 with clinical prognosis and tumor immune infiltration in HNSCC. METHODS: We explored PRF1 expression and its associations with the clinical features of HNSCC via the Tumor Immune Estimation Resource (TIMER), Oncomine and The Cancer Genome Atlas (TCGA) databases. The prognostic value of PRF1 for HNSCC was further explored by Kaplan-Meier plotter and TIMER. Finally, the relation between PRF1 and immune infiltration in HNSCC was estimated via CIBERSORT and TIMER. RESULTS: PRF1 expression was remarkably elevated in HNSCC and associated with clinical stage and HPV infection. High PRF1 expression predicted favorable outcomes in HNSCC, especially in HPV+ HNSCC. Moreover, higher infiltration of CD8+ T cells and CD4+ T cells were found in the PRF1high group of HNSCC. PRF1 expression in HNSCC was strongly correlated with infiltrating CD8+ T cells and dendritic cells (DCs), with higher relevance in HPV+ HNSCC. CONCLUSION: Our findings suggested that PRF1 could be a novel prognostic biomarker in HNSCC and that its expression was related to immune cell infiltration, which was impacted by HPV status.

Associations between PRF1 Ala91Val polymorphism and risk of hemophagocytic lymphohistiocytosis: a meta-analysis based on 1366 subjects.

BACKGROUND: Perforin (PRF1) gene mutation can cause the onset of hemophagocytic lymphohistiocytosis (HLH). It has reported that PRF1 Ala91Val polymorphism was related with HLH risk. In the meta-analysis, we aim to evaluate the association between PRF1 Ala91Val polymorphism and HLH risk. METHODS: We accomplished a meta-analysis of six published case-control studies including 391 patients with HLH and 975 controls. We evaluated the quality of each study through Newcastle-Ottawa Scale (NOS). Data analysis was performed with Stata software. RESULTS: In general, all studies were of high quality (NOS score higher than 7). There were statistically significant between the PRF1 Ala91Val polymorphism and HLH risk though the pooled analysis [for Ala/Val vs. Ala/Ala: pooled odds ratio (OR) = 3.22, 95% confidence interval (CI) 1.08-9.56, P = 0.035, random model; for Ala/Val + Val/Val vs. Ala/Ala: pooled OR = 2.96, 95% CI 1.14-7.69, P = 0.025, random model]. Furthermore, sensitivity analysis also revealed a relationship between PRF1 Ala91Val polymorphism and HLH risk (for Ala/Val vs. Ala/Ala: pooled OR = 5.236, 95% CI 2.72-10.08, P < 0.000, I2 = 12.1%, Pheterogeneity = 0.332; for Ala/Val + Val/Val vs. Ala/Ala, pooled OR = 4.856, 95% CI 2.66-8.85, P < 0.000, I2 = 5.9%, Pheterogeneity = 0.373). Funnel plot and Egger's test did not indicate obvious published bias (P = 0.841 for Ala/Val vs. Ala/Ala; P = 0.284 for Ala/Val + Val/Val vs. Ala/Ala). CONCLUSION: This meta-analysis indicated that PRF1 Ala91Val polymorphism affects the factor for developing HLH and future studies of PRF1 Ala91Val on the onset of HLH will be guaranteed.

Pathogenic Gene Mutations or Variants Identified by Targeted Gene Sequencing in Adults With Hemophagocytic Lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) can be classified into primary HLH and secondary HLH. Primary HLH usually occurs in infants and children with an underlying genetic defect, and there are also teens and occasional adults with primary HLH. Most cases with secondary HLH are adult patients with secondary triggers including infections, malignancies, and autoimmune diseases. The distinction between primary HLH and secondary HLH seems to be less straightforward, as patients with secondary HLH may also have genetic defects while primary HLH can be triggered by secondary causes. In this study, using amplicon-based targeted gene sequencing (TGS), we sequenced eighteen HLH-related genes in 112 adult HLH cases, which were mostly secondary HLH. Mutations or rare variants were identified in 48 cases (42.9%). All the variants except one were missense variants, and biallelic gene mutations were identified in 3 cases in which only one case harbored homogenous missense mutation. Recurrent variants including UNC13D p.G863D and AP3B1 p.T359A are much more prevalent in our cohort than in normal East Asian population, and in silico analysis predicted pathogenicity of these variants. In conclusion, according to our study, genetic defects may also contribute to the development of adult HLH cases or secondary HLH cases.

Rare cause of Hemophagocytic Lymphohistiocytosis due to mutation in PRF1 and SH2D1A genes in two children - a case report with a review.

BACKGROUND: Hemophagocytic Lymphohistiocytosis (HLH) is a rare, complex, life-threatening hyper-inflammatory condition due to over activation of lymphocytes mediated secretory cytokines in the body. It occurs as a primary HLH due to genetic defect that mostly occurs in the childhood and associated with early neonatal death. Secondary HLH is triggered by secondary to infection and can occur at any age. CASE PRESENTATION: The current report presents two cases of HLH. Case 1, three-months-old boy born to second degree consanguineous parents was clinically suspected with HLH. A pathogenic variant in exon 2 of PRF1 gene [c.386G > C (p.Trp129Ser); FLH-type2] was detected. The parents and the fetus under investigation were shown to be heterozygous carriers, while Case-1 was homozygous for the said variant. Case 2, a one and half-year old male child referred for work-up was born to non-consanguineous young parents. His HLH suspicion was in accordance with HLH-2004 Revised diagnostic guidelines (fulfilling 5/8 criteria). Molecular study revealed hemizygous likely pathogenic variant c.138-3C > G in intron 1 of SH2D1A gene. Both the mother and younger sister were confirmed to be the carrier of the same variant. CONCLUSION: This study has represented two rare cases of HLH carrying missense variant in PRF1 and splice site variant in SH2D1A gene. Detailed molecular analysis has helped the families with precise genetic counselling and prenatal diagnosis during subsequent pregnancy. It is advocated that male patients presenting with EBV-associated HLH may be screened for XLP that may lead to early diagnosis and therapeutic implication if any.