A prospective evaluation of degranulation assays in the rapid diagnosis of familial hemophagocytic syndromes. Blood. 2012;119:2754-2763. [PMID: 22294731 DOI: 10.1182/blood-2011-08-374199]

Functional patterns of cytomegalovirus (CMV) pp65 and immediate early-1-specific CD8(+) T cells that are associated with protection from and control of CMV DNAemia after allogeneic stem cell transplantation

BACKGROUND

The functional profile of cytomegalovirus (CMV)-specific CD8(+) T cells that associate with protection from and control of CMV DNAemia in allogeneic stem cell transplant (allo-SCT) recipients remains incompletely characterized.

METHODS

We enumerated pp65 and immediate early (IE)-1-specific CD8(+) T cells expressing interferon-gamma, tumor necrosis factor-alpha, and CD107a, by flow cytometry in 94 patients at days +30 and +60 after allo-SCT.

RESULTS

Fifty of 94 patients had CMV DNAemia within the first 100 days after transplant. CMV-specific CD8(+) T-cell responses (of any functional type) were more likely to be detected in patients who did not display CMV DNAemia than in those who did (P = 0.04). Qualitatively, no major differences in the functional signature of CMV-specific CD8(+) T cells were noted between patients who had or did not have CMV DNAemia. Patients displaying levels of polyfunctional CD8(+) T cells at day +30 >0.30 cell/μL had a lower risk of CMV DNAemia (positive predictive value 76%, and negative predictive value 43%).

CONCLUSION

The presence of polyfunctional CD8(+) T cells (either expressing CD107a or not) was associated with lower levels of CMV replication, and higher frequency of self-resolved episodes. The data reported further clarify the role of polyfunctional CD8(+) T cells in control of CMV DNAemia in allo-SCT recipients.

The syndrome of hemophagocytic lymphohistiocytosis in primary immunodeficiencies: implications for differential diagnosis and pathogenesis

Hemophagocytic lymphohistiocytosis is a hyperinflammatory syndrome defined by clinical and laboratory criteria. Current criteria were created to identify patients with familial hemophagocytic lmyphohistiocytosis in immediate need of immunosuppressive therapy. However, these criteria also identify patients with infection-associated hemophagocytic inflammatory states lacking genetic defects typically predisposing to hemophagocytic lymphohistiocytosis. These patients include those with primary immunodeficiencies, in whom the pathogenesis of the inflammatory syndrome may be distinctive and aggressive immunosuppression is contraindicated. To better characterize hemophagocytic inflammation associated with immunodeficiencies, we combined an international survey with a literature search and identified 63 patients with primary immunodeficiencies other than cytotoxicity defects or X-linked lymphoproliferative disorders, presenting with conditions fulfilling current criteria for hemophagocytic lymphohistiocytosis. Twelve patients had severe combined immunodeficiency with <100/μL T cells, 18 had partial T-cell deficiencies; episodes of hemophagocytic lymphohistiocytosis were mostly associated with viral infections. Twenty-two patients had chronic granulomatous disease with hemophagocytic episodes mainly associated with bacterial infections. Compared to patients with cytotoxicity defects, patients with T-cell deficiencies had lower levels of soluble CD25 and higher ferritin concentrations. Other criteria for hemophagocytoc lymphohistiocytosis were not discriminative. Thus: (i) a hemophagocytic inflammatory syndrome fulfilling criteria for hemophagocytic lymphohistiocytosis can be the initial manifestation of primary immunodeficiencies; (ii) this syndrome can develop despite severe deficiency of T and NK cells, implying that the pathophysiology is distinct and not appropriately described as "lympho"-histiocytosis in these patients; and (iii) current criteria for hemophagocytoc lymphohistiocytosis are insufficient to differentiate hemophagocytic inflammatory syndromes with different pathogeneses. This is important because of implications for therapy, in particular for protocols targeting T cells.

A novel pathogenic variant in PRF1 associated with hemophagocytic lymphohistiocytosis

Familial Hemophagocytic Lymphohistiocytosis type 2 (FHL2) results from mutations in PRF1. We described two unrelated individuals who presented with FHL, in whom severely impaired NK cytotoxicity and decrease perforin expression was observed. DNA sequencing of PRF1 demonstrated that both were not only heterozygous for the p.54R > C/91A > V haplotype but also presented with the novel variant p.47G > V at the perforin protein. Perforin mRNA was found to be increased in a individual with that genotype. A carrier of the novel variant also demonstrated altered perforin mRNA and protein expression. Phylogenetic analysis and multiple alignments with perforin orthologous demonstrated a high level of conservation at Gly47. PolyPhen-2 and PROVEAN predicted p.47G > V to be "probably damaging" and "deleterious", respectively. A thermodynamic analysis showed that this variant was highly stabilizing, decreasing the protein internal energy. The ab initio perforin molecular modeling indicated that Gly47 is buried inside the hydrophobic core of the MACPF domain, which is crucial for the lytic pore formation and protein oligomerization. After the in silico induction of the p.47G > V mutation, Val47 increased the interactions with the surrounding amino acids due to its size and physical properties, avoiding a proper conformational change of the domain. To our knowledge, this is the first description supporting that p.47G > V is a pathogenic variant that in conjunction with p.54R > C/91A > V might result in the clinical phenotype of FHL2.

Malignancy-associated haemophagocytic lymphohistiocytosis in children and adolescents

Haemophagocytic lymphohistiocytosis (HLH) in the context of malignancy is mainly considered a challenge of adult haematology. While this association is also observed in children, little is known regarding inciting factors, appropriate treatment and prognosis. We retrospectively analysed 29 paediatric and adolescent patients for presenting features, type of neoplasm or preceding chemotherapy, treatment and outcome. Haemophagocytic lymphohistiocytosis was considered triggered by the malignancy (M-HLH) in 21 patients, most of whom had T- (n = 12) or B-cell neoplasms (n = 7), with Epstein-Barr virus as a co-trigger in five patients. In eight patients, HLH occurred during chemotherapy (Ch-HLH) for malignancy, mainly acute leukaemias (n = 7); an infectious trigger was found in seven. In M- and Ch-HLH, median overall survival was 1·2 and 0·9 years, and the 6 month survival rates were 67% and 63%, respectively. Seven of 11 deceased M-HLH patients exhibited active malignancy and HLH at the time of death, while only two out of five deceased Ch-HLH patients had evidence of active HLH. To overcome HLH, malignancy- and HLH-directed treatments were administered in the M-HLH cohort; however, it was not possible to determine superiority of one approach over the other. For Ch-HLH, treatment ranged from postponement of chemotherapy to the use of etoposide-containing regimens.

β2-Microglobulin deficiency causes a complex immunodeficiency of the innate and adaptive immune system

BACKGROUND

Most patients with MHC class I (MHC-I) deficiency carry genetic defects in transporter associated with antigen processing 1 (TAP1) or TAP2. The clinical presentation can vary, and about half of the patients have severe skin disease. Previously, one report described β2-microglobulin (β2m) deficiency as another monogenetic cause of MHC-I deficiency, but no further immunologic evaluation was performed.

OBJECTIVE

We sought to describe the molecular and immunologic features of β2m deficiency in 2 Turkish siblings with new diagnoses.

METHODS

Based on clinical and serologic findings, the genetic defect was detected by means of candidate gene analysis. The immunologic characterization comprises flow cytometry, ELISA, functional assays, and immunohistochemistry.

RESULTS

Here we provide the first extensive clinical and immunologic description of β2m deficiency in 2 siblings. The sister had recurrent respiratory tract infections and severe skin disease, whereas the brother was fairly asymptomatic but had bronchiectasis. Not only polymorphic MHC-I but also the related CD1a, CD1b, CD1c, and neonatal Fc receptor molecules were absent from the surfaces of β2m-deficient cells. Absent neonatal Fc receptor surface expression led to low serum IgG and albumin levels in both siblings, whereas the heterozygous parents had normal results for all tested parameters except β2m mRNA (B2M) expression. Similar to TAP deficiency in the absence of a regular CD8 T-cell compartment, CD8(+) γδ T cells were strongly expanded. Natural killer cells were normal in number but not "licensed to kill."

CONCLUSION

The clinical presentation of patients with β2m deficiency resembles that of patients with other forms of MHC-I deficiency, but because of the missing stabilizing effect of β2m on other members of the MHC-I family, the immunologic defect is more extensive than in patients with TAP deficiency.

Incidence and clinical presentation of primary hemophagocytic lymphohistiocytosis in Sweden

BACKGROUND

Primary hemophagocytic lymphohistiocytosis (HLH) represents a group of inherited hyperinflammatory immunodeficiencies, including familial HLH (FHL), Griscelli syndrome type 2 (GS2), and X-linked lymphoproliferative syndrome (XLP). We previously reported an annual incidence of suspected primary HLH in Sweden 1971-1986 of 0.12 per 100,000 children. Here, we determined if the incidence had increased with concomitant awareness.

PROCEDURE

Children <15 years old presenting with HLH 1987-2006 in Sweden were identified through the national mortality registry as well as by nation-wide inquiries to all pediatric centers. HLH was diagnosed according to the HLH-2004 diagnostic guidelines (in case of missing data of at least three of the eight diagnostic criteria, fulfillment of four was sufficient for inclusion). We defined primary HLH as patients presenting with HLH requiring transplantation or dying of disease.

RESULTS

Remarkably, the minimal annual incidence rate of primary HLH remained 0.12 per 100,000 children, equating to 1.8 per 100,000 live births. Notably, an increased overall survival was observed in 1997-2006, relative to the period 1987-1996. During the subsequent 5-year period, 2007-2011, the incidence of genetically and/or functionally verified primary HLH was 0.15 per 100,000 children per year, suggesting that new assays may aid the identification of patients with primary HLH.

CONCLUSION

The annual incidence of primary HLH in Sweden is 0.12-0.15 per 100,000 children per year. Pediatr Blood Cancer 2015;62:346-352. © 2014 Wiley Periodicals, Inc.

γδ T-cell reconstitution after HLA-haploidentical hematopoietic transplantation depleted of TCR-αβ+/CD19+ lymphocytes

We prospectively assessed functional and phenotypic characteristics of γδ T lymphocytes up to 7 months after HLA-haploidentical hematopoietic stem cell transplantation (haplo-HSCT) depleted of αβ(+) T cells and CD19(+) B cells in 27 children with either malignant or nonmalignant disorders. We demonstrate that (1) γδ T cells are the predominant T-cell population in patients during the first weeks after transplantation, being mainly, albeit not only, derived from cells infused with the graft and expanding in vivo; (2) central-memory cells predominated very early posttransplantation for both Vδ1 and Vδ2 subsets; (3) Vδ1 cells are specifically expanded in patients experiencing cytomegalovirus reactivation and are more cytotoxic compared with those of children who did not experience reactivation; (4) these subsets display a cytotoxic phenotype and degranulate when challenged with primary acute myeloid and lymphoid leukemia blasts; and (5) Vδ2 cells are expanded in vitro after exposure to zoledronic acid (ZOL) and efficiently lyse primary lymphoid and myeloid blasts. This is the first detailed characterization of γδ T cells emerging in peripheral blood of children after CD19(+) B-cell and αβ(+) T-cell-depleted haplo-HSCT. Our results can be instrumental to the development of clinical trials using ZOL for improving γδ T-cell killing capacity against leukemia cells. This trial was registered at www.clinicaltrials.gov as #NCT01810120.

B7-H6-mediated downregulation of NKp30 in NK cells contributes to ovarian carcinoma immune escape

In this study the phenotype and function of tumor-associated NK cells from peritoneal fluids of a selected cohort of patients with seropapillary ovarian carcinoma were analyzed. In > 50% of these patients, the expression of the activating receptor NKp30 in tumor-associated NK cells was substantially reduced as compared to autologous peripheral blood (PB) NK cells. The impaired expression of this receptor was associated with the presence of one of its cellular ligands (B7-H6), which was detectable as a surface/cytosolic molecule in tumor cells and as a soluble molecule in the peritoneal fluid. NK cells from patients expressing this NKp30low phenotype displayed an impaired interferon-gamma (IFNγ) production and cytolytic function when tested against target cells expressing surface B7-H6. Our data also suggest that in these patients, the defective expression and function of NKp30 may be induced by the chronic engagement of this receptor by soluble B7-H6 or by tumor cells expressing this ligand. The impairment of NK cell functions described herein could represent a novel mechanism by which the tumor microenvironment may contribute to the escape from immune surveillance.

Hemophagocytic lymphohistiocytosis caused by dominant-negative mutations in STXBP2 that inhibit SNARE-mediated membrane fusion

Familial hemophagocytic lymphohistiocytosis (F-HLH) and Griscelli syndrome type 2 (GS) are life-threatening immunodeficiencies characterized by impaired cytotoxic T lymphocyte (CTL) and natural killer (NK) cell lytic activity. In the majority of cases, these disorders are caused by biallelic inactivating germline mutations in genes such as RAB27A (GS) and PRF1, UNC13D, STX11, and STXBP2 (F-HLH). Although monoallelic (ie, heterozygous) mutations have been identified in certain patients, the clinical significance and molecular mechanisms by which these mutations influence CTL and NK cell function remain poorly understood. Here, we characterize 2 novel monoallelic hemophagocytic lymphohistiocytosis (HLH)-associated mutations affecting codon 65 of STXPB2, the gene encoding Munc18-2, a member of the SEC/MUNC18 family. Unlike previously described Munc18-2 mutants, Munc18-2(R65Q) and Munc18-2(R65W) retain the ability to interact with and stabilize syntaxin 11. However, presence of Munc18-2(R65Q/W) in patient-derived lymphocytes and forced expression in control CTLs and NK cells diminishes degranulation and cytotoxic activity. Mechanistic studies reveal that mutations affecting R65 hinder membrane fusion in vitro by arresting the late steps of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-complex assembly. Collectively, these results reveal a direct role for SEC/MUNC18 proteins in promoting SNARE-complex assembly in vivo and suggest that STXBP2 R65 mutations operate in a novel dominant-negative fashion to impair lytic granule fusion and contribute to HLH.

The unique aspects of presentation and diagnosis of hemophagocytic lymphohistiocytosis in adults

Hemophagocytic lymphohistiocytosis (HLH) was initially described as an inflammatory condition affecting young children but is increasingly diagnosed in adults. Presenting features such as fever, cytopenias, phagocytosis, elevated ferritin, and increased levels of soluble IL-2 receptor are common in both age groups, but the prevalence of several clinical and biochemical criteria differ between pediatric and adult patients. Specifically, an elevated ferritin level does not have the same specificity for HLH in adults, and many other inflammatory conditions need to be considered in the differential. In contrast to the high incidence of infectious triggers seen in pediatric HLH, HLH in adults is often precipitated by a hematologic malignancy. Malignancy-associated HLH has unique manifestations and a uniformly very poor prognosis. Given these differences, diagnostic scoring systems unique to adult HLH have been proposed, and additional prognostic clinical and immunologic parameters are being explored. Although a genetic predisposition is increasingly found to underlie cases of adult-onset HLH, the mutations are less likely to be bi-allelic and differ slightly from those seen in pediatric cases of familial HLH. The facilitating genetic and environmental factors governing presentation of HLH in adults remain elusive. Understanding the clinical aspects and pathophysiology specific to adults with HLH is necessary to tailor therapies derived in pediatric disease to this under-recognized population.

Spectrum of perforin gene mutations in familial hemophagocytic lymphohistiocytosis (FHL) patients in India

BACKGROUND

Inherited perforin deficiency is a rare autosomal recessive disorder that causes severe form of hemophagocytic lymphohistiocytosis (FHL2). The main aim of this study was to analyze the nature of gene mutations in a cohort of Indian patients with FHL2 and to utilize this knowledge for genetic counseling and prenatal diagnosis.

METHODS

13 HLH patients with abnormal perforin expression on NK cells by flow cytometry were included in the study. The entire coding region and intronic splice sites of the PRF1 gene were sequenced from the genomic DNA of these patients.

RESULTS

10 patients from the present series had an early presentation with severe clinical manifestations, while 3 had a delayed onset with unusual presenting features viz Hodgkin's lymphoma, tuberculosis and acute lymphoblastic leukemia. Sequence analysis revealed 11 different mutations (8 novel and 3 previously reported) spread over the entire coding region of PRF1 gene. Missense mutation Trp129Ser in heterozygous state was present in all the 3 patients with a delayed onset of the disease.

CONCLUSION

A wide heterogeneity was observed in the nature of mutations in Indian FHL2 patients. Molecular characterization of PRF1 gene was not only used in the confirmation of diagnosis but also in genetic counseling and pre-natal diagnosis in affected families.

Novel Patient with Late-Onset Familial Hemophagocytic Lymphohistiocytosis with STXBP2 Mutations Presenting with Autoimmune Hepatitis, Neurological Manifestations and Infections Associated with Hypogammaglobulinemia

Familial hemophagocytic lymphohistiocytosis (FHL) is a genetically heterogeneous hyperinflammatory syndrome, caused by an uncontrolled and ineffective proliferation and activation of T-lymphocytes, NK-cells, and macrophages that infiltrate multiple organs. Herein, a patient is presented who suffered from hepatitis and atypical brain lesions. Genetic studies revealed a homozygous mutation in the STXP2 gene; and thus, the diagnosis of FHL5 was confirmed.

Hematopoietic stem cell transplantation of an adolescent with neurological manifestations of homozygous missense PRF1 mutation

Individuals with biallelic truncating PRF1 mutations typically present with fulminant early-onset familial hemophagocytic lymphohistiocytosis (FHL). We report a 19-year-old male with a 5-year history of recurrent fever and headaches progressing to refractory seizures. Brain imaging revealed multiple ring enhancing lesions. Laboratory investigations demonstrated that the patient displayed defective lymphocyte cytotoxicity and carried a homozygous missense PRF1 mutation, c.394G > A (p.Gly132Arg). The patient was successfully treated with chemo-immunotherapy followed by matched related allogeneic hematopoietic stem cell transplantation (HSCT). Our findings demonstrate that prompt HSCT of late-onset FHL with primarily neurological manifestation can reverse central nervous system symptoms and improve long-term outcome.

Laboratory diagnosis of primary immunodeficiencies

Primary immune deficiency disorders represent a highly heterogeneous group of disorders with an increased propensity to infections and other immune complications. A careful history to delineate the pattern of infectious organisms and other complications is important to guide the workup of these patients, but a focused laboratory evaluation is essential to the diagnosis of an underlying primary immunodeficiency. Initial workup of suspected immune deficiencies should include complete blood counts and serologic tests of immunoglobulin levels, vaccine titers, and complement levels, but these tests are often insufficient to make a diagnosis. Recent advancements in the understanding of the immune system have led to the development of novel immunologic assays to aid in the diagnosis of these disorders. Classically utilized to enumerate lymphocyte subsets, flow cytometric-based assays are increasingly utilized to test immune cell function (e.g., neutrophil oxidative burst, NK cytotoxicity), intracellular cytokine production (e.g., TH17 production), cellular signaling pathways (e.g., phosphor-STAT analysis), and protein expression (e.g., BTK, Foxp3). Genetic testing has similarly expanded greatly as more primary immune deficiencies are defined, and the use of mass sequencing technologies is leading to the identification of novel disorders. In order to utilize these complex assays in clinical care, one must have a firm understanding of the immunologic assay, how the results are interpreted, pitfalls in the assays, and how the test affects treatment decisions. This article will provide a systematic approach of the evaluation of a suspected primary immunodeficiency, as well as provide a comprehensive list of testing options and their results in the context of various disease processes.

Importance of hyperbilirubinemia in differentiation of primary and secondary hemophagocytic lymphohistiocytosis in pediatric cases

BACKGROUND AND OBJECTIVE

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyper-inflammatory disease. It is difficult to differentiate between primary and secondary HLH based on clinical findings at the onset of disease. We aimed to find parameters that can help to differentiate primary and secondary HLH at initial diagnosis especially for physicians working in developing countries.

PATIENT AND METHOD

We retrospectively analyzed data of 38 HLH patients who were admitted to the Pediatric Hematology Department of Gaziantep University between January 2009 and December 2013.

RESULTS

Of 38 patients, 20 were defined as primary, and 18 were secondary HLH. The average age of primary and secondary HLH patients was 31±9 and 81±14 months, respectively (p=0.03). We found consanguinity rates significantly higher in primary HLH patients compared to secondary HLH patients (p=0.03). We found that total and direct bilirubin levels significantly increased in primary HLH patients compared to secondary HLH patients (p=0.006, p=0.044). Also, CRP levels were found markedly increased in secondary HLH patients compared to primary ones (p=0.017).

CONCLUSION

We showed that cholestasis and hyperbilirubinemia findings of HLH patients at the initial diagnosis should be considered in favor of primary HLH, and an increased level of CRP should be considered in favor of secondary HLH.

Patients with Griscelli syndrome and normal pigmentation identify RAB27A mutations that selectively disrupt MUNC13-4 binding

BACKGROUND

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare and often fatal disorder characterized by defective cellular cytotoxicity and hyperinflammation, and the only cure known to date is hematopoietic stem cell transplantation. Mutations in RAB27A, LYST, and AP3B1 give rise to FHL associated with oculocutaneous albinism, and patients with FHL are usually only screened for mutations in these genes when albinism is observed. A number of patients with FHL and normal pigmentation remain without a genetic diagnosis.

OBJECTIVE

We asked whether patients with FHL with immunodeficiency but with normal pigmentation might sometimes have mutations that affected cellular cytotoxicity without affecting pigmentation.

METHODS

We carried out mutation analysis of RAB27A, LYST, and AP3B1 in patients with FHL with pigment dilution, as well as a cohort with no clinical evidence of pigment dilution but no mutations in the other known FHL-related genes (PRF1, STXBP2, and UNC13D).

RESULTS

We identify patients with Griscelli syndrome type 2 with biallelic mutations in RAB27A in the absence of albinism. All 6 patients carried mutations at amino acids R141, Y159, or S163 of Rab27a that disrupt the interaction of Rab27a with Munc13-4, without impairing the interaction between melanophilin and Rab27a.

CONCLUSION

These studies highlight the need for RAB27A sequencing in patients with FHL with normal pigmentation and identify a critical binding site for Munc13-4 on Rab27a, revealing the molecular basis of this interaction.

Hemophagocytic syndrome in children and adults

Hemophagocytic syndrome, also known as hemophagocytic lymphohistiocytosis (HLH), is a heterogenic syndrome, which leads to an acute, life-threatening inflammatory reaction. HLH occurs both in children and adults, and can be triggered by various inherited as well as acquired factors. Depending on the etiology, HLH can be divided into genetic (i.e., primary) and acquired (i.e., secondary) forms. Among genetic HLH forms, one can distinguish between familial HLH and other genetically conditioned forms of HLH. Acquired HLH can be typically triggered by infections, autoimmune diseases, and malignancies. The most common symptoms of HLH are unremitting fever, splenomegaly, and peripheral blood cytopenia. Some severely ill patients present with central nervous system involvement. Laboratory tests reveal hyperferritinemia (often >10,000 μg/L), increased serum concentration of soluble receptor α for interleukin-2 (>2,400 U/L), hypertriglyceridemia, hypofibrinogenemia, coagulopathy, hyponatremia, hypoproteinemia, and elevated liver transaminases and bilirubin. Prognosis in HLH is very serious. Genetic HLH is always lethal if adequate therapy is not administered. Similarly, severe acquired cases often lead to death without appropriate treatment. Since HLH can be encountered by various specialists in the medical field, basic knowledge of this entity such as diagnostic criteria and treatment should be familiar to all physicians.

Genetic features of late onset primary hemophagocytic lymphohistiocytosis in adolescence or adulthood

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition of uncontrolled immune activation leading to extreme inflammation. Primary HLH was once believed to be a disease that occurred only in infancy or young children, and was rarely diagnosed in adults. It is now understood that patients can develop primary HLH in their adolescence or adulthood. This study included 252 adolescent and adult patients with a clinical diagnosis of HLH from 35 general medical institutions across mainland China. All exons and 50 bp of flanking intronic sequence of six HLH-related genes (PRF1, UNC13D, STX11, STXBP2, SH2D1A, and BIRC4) were sequenced in these patients. We identified mutations in 18/252 (7.1%) of the patients, with changes in PRF1 being most common. Late-onset HLH often features viral infection and other predisposing factors. We conclude that late-onset primary HLH is not as rare as previously thought. Older patients should not be delayed to receive HLH-related genes testing when they are suspected with HLH.

Towards the targeted management of Chediak-Higashi syndrome

Chediak-Higashi syndrome (CHS) is a rare, autosomal recessive congenital immunodeficiency caused by mutations in CHS1, a gene encoding a putative lysosomal trafficking protein. In the majority of patients, this disorder is typically characterized by infantile-onset hemophagocytic lymphohistiocytosis (HLH), which is lethal unless allogeneic transplantation is performed. A small number of individuals have the attenuated form of the disease and do not benefit from transplant. Improved outcomes of transplantation have been reported when performed before the development of HLH, thus it is important to quickly differentiate patients that present with the childhood form of disease and to prematurely enroll them into a transplantation protocol. In addition, this would also preclude those that exhibit clinical phenotypes of adolescent and adult CHS from this treatment. Patients with an absence of cytotoxic T lymphocyte (CTL) function have a high risk for developing HLH, and could therefore benefit the most from early hematopoietic stem cell transplantation (HSCT). However, although normal CTL cytotoxicity or bi-allelic missense mutations do not exclude the occurrence of HLH in childhood, a more conservative approach is justified. This article summarizes recent advances in the clinical characterization of CHS patients, provides updates on promising new testing methods, and focuses on specific therapeutic approaches.

Hemophagocytic lymphohistiocytosis: Recent progress in the pathogenesis, diagnosis and treatment

Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory syndrome that develops as a primary (familial/hereditary) or secondary (non-familial/hereditary) disease characterized in the majority of the cases by hereditary or acquired impaired cytotoxic T-cell (CTL) and natural killer responses. The molecular mechanisms underlying impaired immune homeostasis have been clarified, particularly for primary diseases. Familial HLH (familial hemophagocytic lymphohistiocytosis type 2-5, Chediak-Higashi syndrome, Griscelli syndrome type 2, Hermansky-Pudlak syndrome type 2) develops due to a defect in lytic granule exocytosis, impairment of (signaling lymphocytic activation molecule)-associated protein, which plays a key role in CTL activity [e.g., X-linked lymphoproliferative syndrome (XLP) 1], or impairment of X-linked inhibitor of apoptosis, a potent regulator of lymphocyte homeostasis (e.g., XLP2). The development of primary HLH is often triggered by infections, but not in all. Secondary HLH develops in association with infection, autoimmune diseases/rheumatological conditions and malignancy. The molecular mechanisms involved in secondary HLH cases remain unknown and the pathophysiology is not the same as primary HLH. For either primary or secondary HLH cases, immunosuppressive therapy should be given to control the hypercytokinemia with steroids, cyclosporine A, or intravenous immune globulin, and if primary HLH is diagnosed, immunochemotherapy with a regimen containing etoposide or anti-thymocyte globulin should be started. Thereafter, allogeneic hematopoietic stem-cell transplantation is recommended for primary HLH or secondary refractory disease (especially EBV-HLH).

Updates on histiocytic disorders

Histiocytic disorders are rare entities that are becoming more recognized as our understanding of the molecular pathogenesis lead to novel diagnostic tests and targeted drug development. A symposium held at the American Society of Pediatric Hematology/Oncology (ASPHO) 2013 Annual Meeting discussed new insights into histiocytic disorders. This review highlights the symposium presentations, divided into three sections encompassing Langerhans cell histiocytosis (LCH), hemophagocytic lymphohistiocytosis (HLH) and Rosai Dorfman disease (RDD) including subsections on pathogenesis, clinical diagnostic criteria and novel insights into treatment. Details of other histiocytic disorders as well as the standard treatment guidelines have been published elsewhere and are beyond the scope of this discussion [Haupt et al. (2013). Pediatr Blood Cancer 60:175-184; Henter et al. (2007). Pediatr Blood Cancer 48:124-131].

Hemophagocytic lymphohistiocytosis in imported pediatric visceral leishmaniasis in a nonendemic area

OBJECTIVES

To describe characteristics of visceral leishmaniasis-associated hemophagocytic lymphohistiocytosis (HLH) with focus on diagnostic clues and pitfalls, including the frequency of central nervous system (CNS) involvement, and to determine the efficacy of liposomal amphotericin B (L-AmB).

STUDY DESIGN

We retrospectively analyzed clinical and laboratory features, diagnostic procedures, and treatment of 13 patients with HLH with imported visceral leishmaniasis, reported to the German HLH reference center (1999-2012).

RESULTS

The spectrum of presentations was indistinguishable from patients with hereditary HLH or with acquired HLH because of infections with other pathogens. In 8 patients, disease onset occurred before the age of 2 years, coinciding with the typical age of manifestation of primary HLH. Two patients had mild nonspecific CNS findings. Misleading antiviral IgM (n = 6) and autoantibodies (n = 2) led to inaccurate interpretation of the etiology of HLH, sometimes with inappropriate therapeutic consequences. False negative results for Leishmania were obtained by initial bone marrow microscopy in 6/13, serology in 1/12, bone marrow culture in 2/5, and polymerase chain reaction of peripheral blood in 1/3 patients, and all bone marrow samples tested were Leishmania-positive by polymerase chain reaction (n = 7). L-AmB was administered to 12 patients, 5 of whom had no prior HLH-directed immunosuppressive therapy; sodium stibogluconate was administered to 1 patient. Persistent remission was achieved in 11 cases. Two patients required repeated or prolonged L-AmB therapy.

CONCLUSIONS

Awareness of diagnostic pitfalls may save patients from unnecessary toxic treatment. CNS involvement is rare. L-AmB shows efficacy in visceral leishmaniasis-associated HLH.

Diagnosing XLP1 in patients with hemophagocytic lymphohistiocytosis

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening, heterogeneous, hyperinflammmatory disorder. Prompt identification of inherited forms resulting from mutation in genes involved in cellular cytotoxicity can be crucial. X-linked lymphoproliferative disease 1 (XLP1), due to mutations in SH2D1A (Xq25) encoding signaling lymphocyte activation molecule-associated protein (SAP), may present with HLH. Defective SAP induces paradoxical inhibitory function of the 2B4 coreceptor and impaired natural killer (NK) (and T) cell response against EBV-infected cells.

OBJECTIVE

To characterize a cohort of patients with HLH and XLP1 for SAP expression and 2B4 function in lymphocytes, proposing a rapid diagnostic screening to direct mutation analysis.

METHODS

We set up rapid assays for 2B4 function (degranulation or (51)Cr-release) to be combined with intracellular SAP expression in peripheral blood NK cells. We studied 12 patients with confirmed mutation in SH2D1A and some family members.

RESULTS

The combined phenotypic/functional assays allowed efficient and complete diagnostic evaluation of all patients with XLP1, thus directing mutation analysis and treatment. Nine cases were SAP(-), 2 expressed SAP with mean relative fluorescence intensity values below the range of healthy controls (SAP(dull)), and 1, carrying the R55L mutation, was SAP(+). NK cells from all patients showed inhibitory 2B4 function and defective killing of B-EBV cells. Carriers with SH2D1A mutations abolishing SAP expression and low percentage of SAP(+) cells showed neutral 2B4 function at the polyclonal NK cell level. Three novel SH2D1A mutations have been identified.

CONCLUSIONS

Study of SAP expression is specific but may have insufficient sensitivity for screening XLP1 as a single tool. Combination with 2B4 functional assay allows identification of all cases.

Hemophagocytic lymphohistiocytosis: review of etiologies and management

Hemophagocytic lymphohistiocytosis (HLH) covers a wide array of related life-threatening conditions featuring ineffective immunity characterized by an uncontrolled hyperinflammatory response. HLH is often triggered by infection. Familial forms result from genetic defects in natural killer cells and cytotoxic T-cells, typically affecting perforin and intracellular vesicles. HLH is likely under-recognized, which contributes to its high morbidity and mortality. Early recognition is crucial for any reasonable attempt at curative therapy to be made. Current treatment regimens include immunosuppression, immune modulation, chemotherapy, and biological response modification, followed by hematopoietic stem-cell transplant (bone marrow transplant). A number of recent studies have contributed to the understanding of HLH pathophysiology, leading to alternate treatment options; however, much work remains to raise awareness and improve the high morbidity and mortality of these complex conditions.

A new functional assay for the diagnosis of X-linked inhibitor of apoptosis (XIAP) deficiency

X-linked inhibitor of apoptosis (XIAP) deficiency, caused by mutations in BIRC4, is an immunodeficiency associated with immune dysregulation and a highly variable clinical presentation. Current diagnostic screening tests such as flow cytometry for XIAP expression or lymphocyte apoptosis assays have significant limitations. Based on recent evidence that XIAP is essential for nucleotide-binding and oligomerization domains (NOD)1/2 signalling, we evaluated the use of a simple flow cytometric assay assessing tumour necrosis factor (TNF) production of monocytes in response to NOD2 stimulation by muramyl dipeptides (L18-MDP) for the functional diagnosis of XIAP deficiency. We investigated 12 patients with XIAP deficiency, six female carriers and relevant disease controls. Irrespective of the diverse clinical phenotype, the extent of residual protein expression or the nature of the mutation, the TNF response was severely reduced in all patients. On average, L18-MDP induced TNF production in 25% of monocytes from healthy donors or female carriers, while fewer than 6% of monocytes responded in affected patients. Notably, the assay clearly discriminated affected patients from disease controls with other immunodeficiencies accompanied by lymphoproliferation, hypogammaglobulinaemia or inflammatory bowel disease. Functional testing of the NOD2 signalling pathway is an easy, fast and reliable assay in the diagnostic evaluation of patients with suspected XIAP deficiency.

Modern management of primary T-cell immunodeficiencies

The study of human T-cell PIDs with Mendelian inheritance has enabled the molecular characterization of important key functions and pathways in T-cell biology. In most cases, T-cell PIDs become apparent as combined T- and B-cell deficiencies. Severe combined immunodeficiencies (SCIDs) are characterized by a complete lack of T-cell development and, in some cases, a developmental block in other lymphoid lineages and manifest within the first year of life. Combined immunodeficiency syndromes (CIDs) result from hypomorphic mutations in typical SCID associated genes or from partial defects of T-cell development and manifest later in childhood by increased susceptibility to infection often combined with disturbances in immune homeostasis, e.g., autoimmunity and increased incidence in lymphoproliferation. The discovery of mutations and characterization of the cellular changes that underlie lymphocyte defects and immune dysregulation have led to novel, specific, successful therapies for severe diseases which are often fatal if left untreated. Over the last few years, impressive progress has been made in understanding the disease mechanisms of T-cell immunodeficiencies and in improving the long-term outcomes of potentially curative treatments, including gene therapy.

Adult haemophagocytic syndrome

Haemophagocytic syndromes (haemophagocytic lymphohistiocytosis) have a wide range of causes, symptoms, and outcomes, but all lead to a hyperinflammatory response and organ damage--mainly reported in paediatric patients, but reports of adult presentation are increasing. Analysis of the genetic and molecular pathophysiology of these syndromes have improved the understanding of the crosstalk between lymphocytes and histiocytes and their regulatoty mechanisms. Clinical presentations with a broad differential diagnosis, and often life-threatening outcome, complicate the management, which might include supportive intensive care, immunosuppressive and biological treatments, or haemopoietic stem cell transplantation. Insufficient knowledge of these syndromes could contribute to poor prognosis. Early diagnosis is essential to initiate appropriate treatment and improve the quality of life and survival of patients with this challenging disorder.

Familial hemophagocytic lymphohistiocytosis: when rare diseases shed light on immune system functioning

The human immune system depends on the activity of cytotoxic T lymphocytes (CTL), natural killer (NK) cells, and NKT cells in order to fight off a viral infection. Understanding the molecular mechanisms during this process and the role of individual proteins was greatly improved by the study of familial hemophagocytic lymphohistiocytosis (FHL). Since 1999, genetic sequencing is the gold standard to classify patients into different subgroups of FHL. The diagnosis, once based on a clinical constellation of abnormalities, is now strongly supported by the results of a functional flow-cytometry screening, which directs the genetic study. A few additional congenital immune deficiencies can also cause a resembling or even identical clinical picture to FHL. As in many other rare human disorders, the collection and analysis of a relatively large number of cases in registries is crucial to draw a complete picture of the disease. The conduction of prospective therapeutic trials allows investigators to increase the awareness of the disease and to speed up the diagnostic process, but also provides important functional and genetic confirmations. Children with confirmed diagnosis may undergo hematopoietic stem cell transplantation, which is the only cure known to date. Moreover, detailed characterization of these rare patients helped to understand the function of individual proteins within the exocytic machinery of CTL, NK, and NKT cells. Moreover, identification of these genotypes also provides valuable information on variant phenotypes, other than FHL, associated with biallelic and monoallelic mutations in the FHL-related genes. In this review, we describe how detailed characterization of patients with genetic hemophagocytic lymphohistiocytosis has resulted in improvement in knowledge regarding contribution of individual proteins to the functional machinery of cytotoxic T- and NK-cells. The review also details how identification of these genotypes has provided valuable information on variant phenotypes.

Prognostic factors and outcomes of adults with hemophagocytic lymphohistiocytosis

OBJECTIVE

To describe the prognostic factors and outcomes of adults with hemophagocytic lymphohistiocytosis (HLH), a rare disorder caused by pathologic activation of the immune system.

PATIENTS AND METHODS

The study population consisted of a consecutive cohort of adult (age ≥18 years) patients treated at Mayo Clinic in Rochester, Minnesota, from January 1, 1996, through December 31, 2011, in whom a diagnosis of HLH was suspected and subsequently confirmed by retrospective review using the HLH-04 diagnostic criteria.

RESULTS

Of 250 adult patients suspected of having HLH, 62 met the HLH-04 diagnostic criteria and were included in the final analysis. The median age was 49 years (range, 18-87 years), and 42 (68%) were male. The underlying cause of HLH was malignant tumor in 32 patients (52%), infection in 21 patients (34%), autoimmune disorder in 5 patients (8%), and idiopathic disease in 4 patients (6%). After a median follow-up of 42 months, 41 patients (66%) had died. The median overall survival of the entire cohort was 2.1 months. The median overall survival of patients with tumor-associated HLH was 1.4 months compared with 22.8 months for patients with non-tumor-associated HLH (P=.01). The presence of a malignant tumor and hypoalbuminemia were significant predictors of inferior survival on multivariate analysis.

CONCLUSION

In this large series of adults with secondary HLH treated at a single tertiary care center, patients with low serum albumin levels and tumor-associated HLH had a markedly worse survival. Hemophagocytic lymphohistiocytosis remains elusive and challenging to clinicians who must maintain a high index of suspicion. The recent discovery of several novel diagnostic and therapeutic modalities may improve outcomes of adult patients with HLH.

Hemophagocytic syndromes--an update

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome and not an independent disease. HLH represents the extreme end of a severe uncontrolled hyperinflammatory reaction that can occur in many underlying conditions. Genetic forms of HLHs are due to defects in transport, processing and function of cytotoxic granules in natural killer cells and cytotoxic T lymphocytes, and are not restricted to manifestation in childhood. Acquired forms of HLH are encountered in infections, autoinflammatory and autoimmune diseases, malignancies, acquired immune deficiency. Functional tests allow for differentiation between genetic and acquired HLH. Treatment aims at suppressing hypercytokinemia and eliminating activated and infected cells. It includes immunomodulatory and immunosuppressive agents, cytostatics, T-cell and cytokine antibodies. In genetic HLH cure can only be achieved with hematopoietic stem cell transplantation. Reduced-intensity conditioning regimens have considerably improved survival.

XLP1 inhibitory effect by 2B4 does not affect DNAM-1 and NKG2D activating pathways in NK cells

X-linked lymphoproliferative disease 1 (XLP1) is a rare congenital immunodeficiency caused by SH2D1A (Xq25) mutations resulting in lack or dysfunction of SLAM-associated protein adaptor molecule. In XLP1 patients, upon ligand (CD48) engagement, 2B4 delivers inhibitory signals that impair the cytolytic activity of NK (and T) cells. This causes the selective inability to control EBV infections and the occurrence of B-cell lymphomas. Here, we show that in the absence of SLAM-associated protein, co-engagement of 2B4 with different activating receptors, either by antibodies or specific ligands on target cells, inhibits different ITAM-dependent signaling pathways including activating killer Ig-like receptors. In XLP1 NK cells, 2B4 affected both the cytolytic and IFN-γ production capabilities, functions that were restored upon disruption of the 2B4/CD48 interactions. Notably, we provide evidence that 2B4 dysfunction does not affect the activity of DNAM-1 and NKG2D triggering receptors. Thus, while CD48(+) B-EBV and lymphoma B cells devoid of NKG2D and DNAM-1 ligands were resistant to lysis, the preferential usage of these receptors allowed XLP1 NK cells to kill lymphomas that expressed sufficient amounts of the specific ligands. The study sheds new light on the XLP1 immunological defect and on the cross-talk of inhibitory 2B4 with triggering NK (and T) receptors.

An N-Terminal Missense Mutation in STX11 Causative of FHL4 Abrogates Syntaxin-11 Binding to Munc18-2

Familial hemophagocytic lymphohistiocytosis (FHL) is an often-fatal hyperinflammatory disorder caused by autosomal recessive mutations in PRF1, UNC13D, STX11, and STXBP2. We identified a homozygous STX11 mutation, c.173T > C (p.L58P), in three patients presenting clinically with hemophagocytic lymphohistiocytosis from unrelated Pakistani families. The mutation yields an amino acid substitution in the N-terminal Habc domain of syntaxin-11 and resulted in defective natural killer cell degranulation. Notably, syntaxin-11 expression was decreased in patient cells. However, in an ectopic expression system, syntaxin-11 L58P was expressed at levels comparable to wild-type syntaxin-11, but did not bind Munc18-2. Moreover, another N-terminal syntaxin-11 mutant, R4A, also did not bind Munc18-2. Thus, we have identified a novel missense STX11 mutation causative of FHL type 4. The syntaxin-11 R4A and L58P mutations reveal that both the N-terminus and Habc domain of syntaxin-11 are required for binding to Munc18-2, implying similarity to the dynamic binary binding of neuronal syntaxin-1 to Munc18-1.

Inhibition of mesenchymal stromal cells by pre-activated lymphocytes and their culture media

Introduction

Despite having a proven immunosuppressive potential in vitro, human mesenchymal stromal cells (MSCs) are reported to display variable efficacy in vivo and, in fact, their proven benefit in the clinical practice is still limited and controversial.

Methods

The interplay between clinical grade MSCs and pre-activated donor lymphocytes or selected lymphocyte subsets was studied in vitro. The kinetics of MSC growth and viability was evaluated by adhesion-dependent changes of culture plate impedance and biochemically by a colorimetric assay. Activation of natural killer (NK) cells was assessed as well, using a flow cytometry assay.

Results

A strong inhibition of MSC growth was rapidly induced by the addition of pre-activated lymphocytes but not of resting lymphocytes. Inhibition seems not to be attributable to a single cell population, as similar results can be obtained by depleting NK cells or by using either selected CD4⁺ or CD8⁺ lymphocytes. In addition, conditioned medium (CM) from activated lymphocytes was able to inhibit MSC growth in a dose-dependent manner. Furthermore, licensing with IFN-γ partially protected MSCs from pre-activated lymphocytes but not from their CM. These results suggest an inhibitory role of lymphocyte-activation-derived substances. However, the identification of a single molecule responsible for MSC inhibition remained elusive, even if preliminary experiments showed that ATP and, to a lesser extent, TNF-α might play a role.

Conclusions

These results suggest that survival of MSCs can be affected by soluble mediators released by activated lymphocytes. Thus it can be hypothesized that MSC immunosuppressive action in vivo could be impaired by ongoing immune activation through the release of inflammatory mediators.

Secondary Hemophagocytic Syndrome: The Importance of Clinical Suspicion

Hemophagocytic syndrome is a rare and potentially fatal disorder characterized by pathological immune activation associated with a primary familial disorder, genetic mutations, or occurring as a sporadic condition. The latter can be secondary to infections, malignancies, or autoimmune diseases. Clinically, patients present signs of severe inflammation, with unremitting fever, cytopenias, spleen enlargement, phagocytosis of bone marrow elements, hypertriglyceridemia, and hypofibrinogenemia. Increased suspicion is determinant to timely initiate treatment in an attempt to alter the natural history. The authors present three clinical cases of this syndrome, with a brief review of the diagnostic criteria and treatment.

Marrow assessment for hemophagocytic lymphohistiocytosis demonstrates poor correlation with disease probability

OBJECTIVES

To evaluate the amount of hemophagocytosis in 64 marrow core biopsy specimens and aspirates from 58 patients with clinical suspicion for secondary hemophagocytic lymphohistiocytosis (HLH) or reported findings of hemophagocytosis.

METHODS

A review of medical records assigned patients to a low-risk (45 patients) or high-risk (13 patients) HLH group, and association with histologic findings was examined using the Fisher exact test.

RESULTS

The amount of hemophagocytosis in aspirate or the core biopsy specimen did not correlate with disease probability (P = .17 and P = .63, respectively). Of the clinical/laboratory criteria assessed, the most significant correlations with HLH were highly elevated ferritin (P = .01), cytopenias (P = .02), and fever (P = .009).

CONCLUSIONS

Our findings indicated that marrow histologic findings alone do not reliably predict the probability of HLH, and an isolated finding of hemophagocytosis, even when present in a high amount, lacks specificity for HLH.

Syntaxin binding mechanism and disease-causing mutations in Munc18-2

Mutations in either syntaxin 11 (Stx11) or Munc18-2 abolish cytotoxic T lymphocytes (CTL) and natural killer cell (NK) cytotoxicity, and give rise to familial hemophagocytic lymphohistiocytosis (FHL4 or FHL5, respectively). Although Munc18-2 is known to interact with Stx11, little is known about the molecular mechanisms governing the specificity of this interaction or how in vitro IL-2 activation leads to compensation of CTL and NK cytotoxicity. To understand how mutations in Munc18-2 give rise to disease, we have solved the structure of human Munc18-2 at 2.6 Å resolution and mapped 18 point mutations. The four surface mutations identified (R39P, L130S, E132A, P334L) map exclusively to the predicted syntaxin and soluble N-ethylmaleimide-sensitive factor accessory protein receptor binding sites of Munc18-2. We find that Munc18-2 binds the N-terminal peptide of Stx11 with a ~20-fold higher affinity than Stx3, suggesting a potential role in selective binding. Upon IL-2 activation, levels of Stx3 are increased, favoring Munc18-2 binding when Stx11 is absent. Similarly, Munc18-1, expressed in IL-2-activated CTL, is capable of binding Stx11. These findings provide potential explanations for restoration of Munc18-Stx function and cytotoxicity in IL-2-activated cells.

Treosulfan-based conditioning regimen for children and adolescents with hemophagocytic lymphohistiocytosis

In hematopoietic stem cell transplantation for hemophagocytic lymphohistiocytosis, high transplant-related mortality after busulfan-based myeloablative regimens has been observed. Conditioning regimens with reduced toxicity based on melphalan or treosulfan are promising alternatives. We retrospectively analyzed hematopoietic stem cell transplantations in 19 hemophagocytic lymphohistiocytosis patients after conditioning with fludarabine, treosulfan, alemtuzumab, with or without thiotepa. Overall and disease-free survivals were 100% (follow up 7-31 months). Two patients required second transplant (1 after haploidentical transplantation). In 6 patients, overall donor chimerism dropped below 75% and prompted donor lymphocyte infusions. Administration of donor lymphocytes or second transplantation were significantly more frequent after transplantation from a human leukocyte antigen mismatched (9/10) versus matched (10/10) donor (P=0.018). The toxicity profile was favorable, with one veno-occlusive disease, one grade 3 graft-versus-host disease after donor lymphocyte infusion, and 2 severe viral infections (1 influenza, 1 Epstein Barr virus). In conclusion, the treosulfan-based regimen in hemophagocytic lymphohistiocytosis is effective with low toxicity and gives excellent overall and disease-free survival rates. In the future, the incidence of mixed chimerism, particularly after human leukocyte antigen mismatched donor transplants, needs to be addressed.

X-linked inhibitor of apoptosis (XIAP) deficiency: the spectrum of presenting manifestations beyond hemophagocytic lymphohistiocytosis

X-linked inhibitor of apoptosis (XIAP) deficiency caused by mutations in BIRC4 was initially described in patients with X-linked lymphoproliferative syndrome (XLP) who had no mutations in SH2D1A. In the initial reports, EBV-associated hemophagocytic lymphohistiocytosis (HLH) was the predominant clinical phenotype. Among 25 symptomatic patients diagnosed with XIAP deficiency, we identified 17 patients who initially presented with manifestations other than HLH. These included Crohn-like bowel disease (n=6), severe infectious mononucleosis (n=4), isolated splenomegaly (n=3), uveitis (n=1), periodic fever (n=1), fistulating skin abscesses (n=1) and severe Giardia enteritis (n=1). Subsequent manifestations included celiac-like disease, antibody deficiency, splenomegaly and partial HLH. Screening by flow cytometry identified 14 of 17 patients in our cohort. However, neither genotype nor protein expression nor results from cell death studies were clearly associated with the clinical phenotype. Only mutation analysis can reliably identify affected patients. XIAP deficiency must be considered in a wide range of clinical presentations.

Defects in neutrophil granule mobilization and bactericidal activity in familial hemophagocytic lymphohistiocytosis type 5 (FHL-5) syndrome caused by STXBP2/Munc18-2 mutations

Neutrophils of patients with FHL-5 with Munc18-2/STXBP2 mutations have impaired granule fusion and bacterial killing.

Novel mutations in the UNC13D gene carried by a Chinese neonate with hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) in different ethnicities has been described in the literature, but few cases in patients of Chinese descent have been reported. Here, we describe the case of a Chinese neonate presenting with HLH carrying novel, compound heterozygous mutations of the UNC13D gene, including [c.2295_2298delGCAG, p.Glu765Aspfs*27] in exon 23, c.-250C>T, c.1+30G>A, c.279C>T, c.888G>C, c.18+36A>G, c.20-48T>C, c.1977C>T, c.2296C>T, c.24-46C>T, c.26-9_26-8insC, c.2599A>G, c.28+48C>T and c.3198A>G, some of which have not been reported in the literature. Cytokine profile analyses were performed in this patient, and the results were consistent with our previous findings in HLH patients. Cytokine profile monitoring may be helpful in differentiating among various clinical phases of HLH.

Variations of the UNC13D gene in patients with autoimmune lymphoproliferative syndrome

Autoimmune lymphoproliferative syndrome (ALPS) is caused by genetic defects decreasing Fas function and is characterized by lymphadenopathy/splenomegaly and expansion of CD4/CD8 double-negative T cells. This latter expansion is absent in the ALPS variant named Dianzani Autoimmune/lymphoproliferative Disease (DALD). In addition to the causative mutations, the genetic background influences ALPS and DALD development. We previously suggested a disease-modifying role for the perforin gene involved in familial hemophagocytic lymphohistiocytosis (FHL). The UNC13D gene codes for Munc13-4, which is involved in perforin secretion and FHL development, and thus, another candidate for a disease-modifying role in ALPS and DALD. In this work, we sequenced UNC13D in 21 ALPS and 20 DALD patients and compared these results with sequences obtained from 61 healthy subjects and 38 multiple sclerosis (MS) patients. We detected four rare missense variations in three heterozygous ALPS patients carrying p.Cys112Ser, p.Val781Ile, and a haplotype comprising both p.Ile848Leu and p.Ala995Pro. Transfection of the mutant cDNAs into HMC-1 cells showed that they decreased granule exocytosis, compared to the wild-type construct. An additional rare missense variation, p.Pro271Ser, was detected in a healthy subject, but this variation did not decrease Munc13-4 function. These data suggest that rare loss-of-function variations of UND13D are risk factors for ALPS development.