Correlation between phenotypic heterogeneity and gene mutational characteristics in familial hemophagocytic lymphohistiocytosis (FHL)

Co-Occurrence of Familial Hemophagocytic Lymphohistiocytosis Type 2 and Chronic Active Epstein-Barr Virus in Adulthood

We report, to the best of our best knowledge, the oldest individual to ever be diagnosed with Familial Hemophagocytic Lymphohistiocytosis (FHL) Type 2 from homozygous c.1349C>T (p.T450M) missense variants in the PRF1 gene. This rare case advanced in complexity with a simultaneous diagnosis of Chronic Active Epstein-Barr Virus (CAEBV) - a distinct clinical entity from acute EBV infections and a well-described trigger of Hemophagocytic Lymphohistiocytosis (HLH). This is, to the best of our knowledge, the only individual to ever be diagnosed with CAEBV in the setting of this specific variant and the oldest to be diagnosed with a coexisting perforin variant. This case provides understanding of EBV, human genetics, and lymphoproliferative disorders while adding a unique differential diagnosis to adults who present with fever of unknown origin and diffuse lymphadenopathy without evidence of malignancy. This report explores the diagnosis and treatment of both HLH and CAEBV, encouraging discussion regarding current clinical management and future research needs.

Genetic variant spectrum in 265 Chinese patients with hemophagocytic lymphohistiocytosis: Molecular analyses of PRF1, UNC13D, STX11, STXBP2, SH2D1A, and XIAP

Hemophagocytic lymphohistiocytosis (HLH) is a rare life-threatening hyperinflammatory disease. This study aimed to investigate the frequencies and distributions of inherited variants in PRF1, UNC13D, STX11, STXBP2, SH2D1A, and XIAP genes in Chinese patients with HLH. A total of 265 patients diagnosed with HLH from January, 2010 to December, 2016 were recruited and analyzed for the 6 genes. Genetic variants were observed in 87 (32.83%) patients. 36 (13.58%) exhibited variants in UNC13D, 18 (6.79%) exhibited PRF1 variants, 10 (3.77%) had variants in XIAP, 9 (3.40%) exhibited variants in STXBP2, 6 (2.26%) carried variants in SH2D1A, 1 (0.38%) had STX11 variant, and 7 (2.64%) exhibited digenic variants. Monoallelic variants were the most common, which accounted for 49.43% of all cases with variants. All variants were confirmed to be germline-derived. The present study describes a distinct variant spectrum in Chinese patients with HLH, whereby UNC13D is the most frequently mutated gene with missense variants that are the most common molecular defects. The variant profile of Chinese HLH patients is quite different from that of Western cohorts but similar to that of Korean patients, yet showing its own uniqueness. This racial difference shows the role of genetic background in the occurrence of HLH.

Primary hemophagocytic lymphohistiocytosis in adults: the utility of family surveys in a single-center study from China

Background

This study investigated the clinical characteristics of primary hemophagocytic lymphohistiocytosis (HLH) in adults, including immunological markers, pedigree findings, and conditions of allogeneic hematopoietic stem cell transplantation (Allo-HSCT).

Methods

The study included clinical data of 18 adult patients with primary HLH treated in our center from June 2010 to January 2017.

Results

Of these 18 cases, pathogenic variants were found in the following genes: PRF1 (n = 11), UNC13D (n = 5), SH2D1A (n = 2), RAB27a (n = 1), and LYST (n = 2). One patient had pathogenic variants in both PRF1 and UNC13D genes, one patient had pathogenic variants in both LYST and UNC13D genes and another patient had pathogenic variants in both PRF1 and SH2D1A genes. Additionally, 3 of the 18 cases involved homozygous pathogenic variants, while 2 cases involved hemizygous pathogenic variants. The remaining 13 cases involved compound heterozygous pathogenic variants. The natural killer (NK) cell activity test was conducted in all 18 cases where 14(77.8%)patients showed reduction in NK cell activity. Furthermore, this article presents 3 representative results of the pedigree findings from 12 patients who underwent family surveys. The 8 patients who underwent Allo-HSCT had a median survival of 27.2 months, as compared with the median survival of 7 months for the10 patients who did not undergo Allo-HSCT, a significant difference between the two groups of patients (p = 0.006).

Conclusion

PRF1 was one of the most commonly mutated gene in adult patients with primary HLH. Family surveys and immunological markers were important for the HLH diagnosis and the selection of an appropriate donor. Allo-HSCT was an effective therapy for adult primary HLH.

Hemophagocytic Lymphohistiocytosis

Hemophagocytic lymphohistiocytosis is a life-threatening disorder characterized by unbridled activation of cytotoxic T lymphocytes, natural killer (NK) cells, and macrophages resulting in hypercytokinemia and immune-mediated injury of multiple organ systems. It is seen in both children and adults and is recognized as primary (driven by underlying genetic mutations that abolish critical proteins required for normal function of cytotoxic T cells and NK cells) or secondary (resulting from a malignant, infectious, or autoimmune stimulus without an identifiable underlying genetic trigger). Clinical and laboratory manifestations include fever, splenomegaly, neurologic dysfunction, coagulopathy, liver dysfunction, cytopenias, hypertriglyceridemia, hyperferritinemia, hemophagocytosis, and diminished NK cell activity. It is treated with immune suppressants, etoposide, and allogeneic hematopoietic stem cell transplantation; more than 50% of children who undergo transplant survive, but adults have quite poor outcomes even with aggressive management. Newer agents directed at subduing the uncontrolled immune response in a targeted fashion offer promise in this highly morbid disease.

Clinical utility of soluble interleukin-2 receptor in hemophagocytic syndromes: a systematic scoping review

The serum-soluble interleukin-2 receptor (sIL-2r) level is considered an important diagnostic test and disease marker in hemophagocytic syndromes/hemophagocytic lymphohistiocytosis (HPS/HLH). However, this cytokine receptor is rarely measured in clinical practice and has been excluded from recent diagnostic/classification criteria such as the HScore and macrophage activation syndrome (MAS) 16. We performed a systematic scoping review of 64 articles (1975-2016) examining the clinical utility of sIL-2r in HPS/HLH. Twenty-two articles describe sIL-2r as a sensitive diagnostic marker for HLH, but only three distinct datasets actually address sensitivity. The original HLH-2004 Guidelines reported sensitivity of 93% and specificity of 100% for sIL-2r ≥ 2400, based on a pediatric dataset (n = 152) which is published for the first time in this review. Two pediatric studies reported sensitivity of 89% for sIL-2r ≥ 2400 in diagnosis of MAS complicating juvenile idiopathic arthritis (JIA) (n = 27) and 88% for secondary HLH in acute liver failure (n = 9). Twenty articles described sIL-2r as a dynamic marker of disease activity that falls with response to treatment, and 15 described high initial sIL-2r levels >10,000 U/mL as a poor prognostic marker. The ability of sIL-2r to distinguish between subtypes of HPS/HLH was inconsistent. This review confirms the importance of soluble IL-2r as a diagnostic and disease marker in HPS/HLH, but also reveals the need for more primary data about its performance characteristics, particularly in adults. More emphasis should be made in including this simple, inexpensive test in clinical practice and studies of HPS/HLH.

Exome sequencing for simultaneous mutation screening in children with hemophagocytic lymphohistiocytosis

In the present study, we used exome sequencing to analyze PRF1, UNC13D, STX11, and STXBP2, as well as genes associated with primary immunodeficiency disease (RAB27A, LYST, AP3B1, SH2D1A, ITK, CD27, XIAP, and MAGT1) in Thai children with hemophagocytic lymphohistiocytosis (HLH). We performed mutation analysis of HLH-associated genes in 25 Thai children using an exome sequencing method. Genetic variations found within these target genes were compared to exome sequencing data from 133 healthy individuals. Variants identified with minor allele frequencies <5% and novel mutations were confirmed using Sanger sequencing. Exome sequencing data revealed 101 non-synonymous single nucleotide polymorphisms (SNPs) in all subjects. These SNPs were classified as pathogenic (n = 1), likely pathogenic (n = 16), variant of unknown significance (n = 12), or benign variant (n = 72). Homozygous, compound heterozygous, and double-gene heterozygous variants, involving mutations in PRF1 (n = 3), UNC13D (n = 2), STXBP2 (n = 3), LYST (n = 3), XIAP (n = 2), AP3B1 (n = 1), RAB27A (n = 1), and MAGT1 (n = 1), were demonstrated in 12 patients. Novel mutations were found in most patients in this study. In conclusion, exome sequencing demonstrated the ability to identify rare genetic variants in HLH patients. This method is useful in the detection of mutations in multi-gene associated diseases.

Hereditary and acquired hemophagocytic lymphohistiocytosis

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a rare but life-threatening hyperinflammatory/hypercytokinemia syndrome clinicopathologically manifested by fever, hepatosplenomegaly, cytopenias, liver dysfunction, and hemophagocytosis.

METHODS

We searched the medical literature for English-written articles and analyzed data regarding the diagnosis, pathoetiology, prognosis, and management of HLH.

RESULTS

HLH can be subcategorized into primary/genetic (PHLH) or secondary/acquired (SHLH) according to etiology. PHLH, including familial HLH and inherited immune deficiency syndromes, typically occurs in children harboring underlying genetic defects, whereas SHLH frequently manifests in adults and is associated with infection, autoimmunity, immune suppression, or malignancy. The pathogenesis of HLH is still elusive. Its known mechanisms include somatic mutations in gene coding for proteins implicated in the cytotoxic pathways of cytotoxic T or natural killer cells. The impaired ability of these cells to kill target cells leads to an uncontrolled hypercytokinemia and hyperinflammatory process, triggering hemophagocytosis and multiorgan failure. Corticosteroids, chemotherapy, and immunotherapy are the mainstay therapeutic strategies. The consolidation with allogeneic hematopoietic stem cell transplantation is a potentially curative option for PHLH and refractory or relapsed SHLH.

CONCLUSIONS

Understanding of the pathophysiology of HLH has improved in the last decade. The establishment of diagnostic and treatment guidelines for PHLH and SHLH has resulted in earlier diagnoses and the rapid initiation of therapy, both of which are associated with favorable outcomes.

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.

Perforin gene mutations in 77 Chinese patients with lymphomas

BACKGROUND:

Perforin gene (PRF1) mutations have been reported in patients with lymphoma, but the prevalence and characteristics of PRF1 mutation have not been identified in Chinese patients with lymphoma.

METHODS:

Seventy-seven patients with lymphoma, including 6 patients with Hodgkin lymphoma and 71 patients with non-Hodgkin lymphoma, were recruited. DNA samples from peripheral blood were used for PRF1 mutation detection by the PCR-sequencing method.

RESULTS:

Eleven novel PRF1 mutations were found in 8 of the 77 patients with lymphoma. Biallelic or compound monoallelic missense mutations in 3 patients indicated the severe impairment of perforin function, monoallelic missense mutations in 3 patients possibly contributed a genetic predisposition to malignancies, and synonymous mutations in 2 patients showed unknown significance.

CONCLUSIONS:

The frequency of EBV infection was similar in lymphoma patients with PRF1 mutations and those without the mutations. The same PRF1 mutations were also found in DNA samples from nails or hair follicles from 4 patients with PRF1 mutations, suggesting that these mutations may be of germ-line origin.

Clinical features, genetics, and outcome of pediatric patients with hemophagocytic lymphohistiocytosis in Korea: report of a nationwide survey from Korea Histiocytosis Working Party

Background

We analyzed a nationwide registry of pediatric patients with hemophagocytic lymphohistiocytosis (HLH) in Korea to assess the clinical and genetic features and treatment outcomes in pediatric HLH.

Methods

The Korea Histiocytosis Working Party retrospectively analyzed data on 251 pediatric patients diagnosed with HLH between 1996 and 2011.

Results

In the study cohort, 25 cases were categorized with familial HLH, 64 with presumed secondary HLH, and 162 with unspecified HLH. Of 217 evaluable patients, 91 (42%) had concomitant Epstein–Barr virus infection. Of 238 evaluable patients, central nervous system (CNS) involvement, which was more frequent in the familial group, was evident in 81 cases (34%). Genetic tests revealed a predominant UNC13D mutation with a high incidence of two recurrent splicing mutations (c.118‐308C>T and c.754‐1G>C). The 5‐yr overall survival rate was 68% (38% in the familial group and 81% in the presumed secondary group). The 5‐yr overall survival rate among 32 patients who underwent allogeneic hematopoietic stem cell transplantation was 64%. In multivariate analysis, a younger age at diagnosis, severe transaminasemia, and a coagulation abnormality were independent prognostic factors for survival. Responses during initial treatments were also significant indicators of outcome.

Conclusion

Our study showed the unique predominance of a UNC13D mutation and vulnerability to Epstein–Barr virus infection in Korean children with HLH and emphasizes the prognostic significance of age, liver dysfunction, and treatment responses in this disease. A multicenter prospective trial that builds on the present results is warranted to identify subgroups of patients with a poor prognosis and identify optimal treatments.

Hemophagocytic Syndrome and Critical Illness: New Insights into Diagnosis and Management

Hemophagocytic lymphohistiocytosis (HLH) comprises a heterogeneous group of diseases that are characterized by a hyperinflammatory state due to uncontrolled T cell, macrophage, and histiocyte activation, accompanied by excessive cytokine production. This rare condition is almost uniformly fatal unless promptly recognized and treated. Much progress has been made in the last two decades in our understanding of the mechanisms underlying familial, and to a lesser extent, acquired cases of HLH. Recurrent mutations in more than 10 different genes have now been identified, involving biological pathways converging on intracellular vesicle trafficking and cytolytic granule exocytosis. Mechanisms underlying the majority of patients with acquired HLH, however, remain elusive, hampering both diagnostic evaluation and therapeutic management of these patients. Given that the majority of intensive care unit (ICU) patients with sepsis or multiorgan failure share many features of HLH, it is especially critical for pediatric and adult intensivists to be able to recognize patients with bona fide HLH and initiate treatment without delay. In this article, we review our current understanding of the pathophysiology, clinical testing, diagnosis, and treatment of patients with HLH, especially as it pertains to the care of critically ill patients in pediatric and medical ICUs.

Advances in understanding the pathogenesis of HLH

Haemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory disorder resulting from immune dysfunction reflecting either primary immune deficiency or acquired failure of normal immune homeostasis. Familial HLH includes autosomal recessive and X-linked disorders characterized by uncontrolled activation of T cells and macrophages and overproduction of inflammatory cytokines, secondary to defects in genes encoding proteins involved in granule-dependent cytolytic pathways. In older children and adults, HLH is associated more often with infections, malignancies, autoimmune diseases, and acquired immune deficiencies. HLH, macrophage activation syndrome, sepsis, and systemic inflammatory response syndrome are different clinical entities that probably represent a common immunopathological state, termed cytokine storm. These conditions may be clinically indistinguishable; all include massive inflammatory response, elevated serum cytokine levels, multi-organ involvement, haemophagocytic macrophages, and often death. Tissues of haematopoietic and lymphoid function are directly involved; other organs are secondarily damaged by circulating cytokines and chemokines. Haemophagocytic disorders are now increasingly diagnosed in the context of severe inflammatory reactions to viruses, malignancies and systemic connective tissue diseases. Many of these cases may reflect underlying genetic predispositions to HLH. The detection of gene defects has contributed considerably to our understanding of HLH, but the mechanisms leading to acquired HLH have yet to be fully determined.

Are all mutant SNARES equal?

In this issue of Blood, Pagel et al carefully deliniate some fascinating phenotype/genotype correlations in a larger cohort than in their earlier reports of familial hemophagocytic lymphohistiocytosis (HLH).

Analyses of the PRF1 gene in individuals with hemophagocytic lymphohystiocytosis reveal the common haplotype R54C/A91V in Colombian unrelated families associated with late onset disease

Familial hemophagocytic lymphohistiocytosis (FHL), is a rare autosomal recessive disorder characterized by an impairment of cytotoxic cells and uncontrolled activation of macrophages. This study presents the first description of four patients with FHL type 2 in Latin America. Patient 1 fulfilled the disease diagnostic criteria since 2 months of age, whereas patients 2, 3 and 4 exhibited the typical manifestations of the disease only later in their childhood. The PRF1 genetic analysis in these patients revealed two previously reported mutations: L17fsx50 and R54C. Interestingly, seven out of the 8 alleles evaluated here in patients carried the haplotype R54C/A91V, suggesting that this is a highly frequent FHL type 2 allele in Colombia. This haplotype confers residual cytotoxic function leading to late onset disease. Therefore, this report highlights the remarkable complexity of FHL diagnostic, emphasizing the importance of the genetic characterization of the disease.

Inherited defects causing hemophagocytic lymphohistiocytic syndrome

Hemophagocytic lymphohistiocytosis (HLH) manifests as the uncontrolled activation of T lymphocytes and macrophages infiltrating multiple organs. Molecular studies of individuals with HLH have demonstrated in most of these conditions a critical role of granule-dependent cytotoxic activity in the regulation of lymphocyte homeostasis, and have allowed the characterization of key effectors regulating cytotoxic granule release. The cytolytic process may now be considered a multistep process, including cell activation; the polarization of cytotoxic granules toward the conjugated target cell; the tethering, priming, and fusion of the cytotoxic granules with the plasma membrane; and the release of their contents (perforin and granzymes) into the intercellular cleft, leading to target cell death. Cytolytic cells have a second effector function involving the production of cytokines, principally γ-interferon, which is secreted independently of the exocytosis cytotoxic granule pathway. An analysis of the mechanisms underlying HLH has identified γ-interferon as a key cytokine inducing uncontrolled macrophage activation, and thus represents a potential therapeutic target.

Familial hemophagocytic lymphohistiocytosis: a model for understanding the human machinery of cellular cytotoxicity

Cytotoxic T lymphocytes, natural killer cells, and NKT cells are effector cells able to kill infected cells. In some inherited human disorders, a defect in selected proteins involved in the cellular cytotoxicity mechanism results in specific clinical syndromes, grouped under the name of familial hemophagocytic lymphohistiocytosis. Recent advances in genetic studies of these patients has allowed the identification of different genetic subsets. Additional genetic immune deficiencies may also induce a similar clinical picture. International cooperation and prospective trials resulted in refining the diagnostic and therapeutic approach to these rare diseases with improved outcome but also with improved knowledge of the mechanisms underlying granule-mediated cellular cytotoxicity in humans.

Disruption of MyD88 signaling suppresses hemophagocytic lymphohistiocytosis in mice

Hemophagocytic lymphohistiocytosis (HLH) is a rare inflammatory disorder with a poor prognosis for affected individuals. To find a means of suppressing the clinical phenotype, we investigated the cellular and molecular mechanisms leading to HLH in Unc13d(jinx/jinx) mice, in which cytolytic function of NK and CD8(+) T cells is impaired. Unc13d(jinx/jinx) mutants infected with lymphochoriomeningitis virus (LCMV) present typical clinical features of HLH, including splenomegaly, elevated serum IFNγ, and anemia. Proteins mediating cell-cell contact, cytokine signaling or Toll-like receptor (TLR) signaling were analyzed. We show that neither the integrin CD18, which is involved in adhesion between antigen-presenting cells and effector T cells, nor tumor necrosis factor (TNF) made nonredundant contributions to the disease phenotype. Disruption of IFNγ signaling reduced immune cell activation in Unc13d(jinx/jinx) mice, but also resulted in uncontrolled viral proliferation and exaggerated release of inflammatory cytokines. Abrogating the function of myeloid differentiation primary response gene 88 (MyD88) in Unc13d(jinx/jinx) mice suppressed immune cell activation and controlled cytokine production in an IL-1 receptor 1 (IL-1R1)-independent way. Our findings implicate MyD88 as the key initiator of myeloid and lymphoid proliferation in HLH, and suggest that blockade of this signaling molecule may reduce immunopathology in patients.

Chlamydia pneumoniae infection-related hemophagocytic lymphohistiocytosis and acute encephalitis and poliomyelitis-like flaccid paralysis

A 3-year-old male presented with Chlamydia pneumoniae infection-related hemophagocytic lymphohistiocytosis (HLH). The patient developed an episode of HLH with severe skin eruption following C. pneumoniae pneumonia. Symptoms responded to steroid/cyclosporine A therapy, but the patient slowly lost consciousness and developed systemic flaccid paralysis. He was diagnosed with encephalitis/myelitis by brain and spinal MRI. Neurological symptoms and signs gradually resolved. We thought that the immune response to C. pneumoniae infection triggered the development of HLH, associated with unusual neurological complications. This report describes a novel case of C. pneumoniae-associated HLH and with poliomyelitis like flaccid paralysis.

Familial haemophagocytic lymphohistiocytosis: advances in the genetic basis, diagnosis and management

Familial haemophagocytic lymphohistiocytosis (FHL) is a rare autosomal recessive disorder of immune dysregulation associated with uncontrolled T cell and macrophage activation and hypercytokinaemia. The incidence of FHL is 0·12/100·000 children born per year, with a male to female ratio of 1:1. The disease is classified into six different types based on genetic linkage analysis and chromosomal localization; five specific genetic defects have been identified, which account for approximately 90% of all patients. Type 1 is due to an as yet unidentified gene defect located on chromosome nine. Type 2 is caused by mutations in the perforin (PRF1) gene, type 3 by mutations in the Munc-13-4 (UNC13D) gene, type 4 by mutations in the syntaxin 11 (STX11) gene and the recently described type 5 due to mutations in the gene encoding syntaxin binding protein 2 (STXBP-2). The incidence of the five types varies in different ethnic groups. The most common presenting features are pyrexia of unknown origin, pronounced hepatosplenomegaly and cytopenias. Neurological features tend to present later and are associated with poor prognosis. Absent or decreased lymphocyte cytotoxicity is the cellular hallmark of FHL. Biochemical features such as hyperferritinaemia, hypertriglyceridaemia and hypofibrinogenaemia are usually present, along with high levels of soluble interleukin 2 receptor in the blood and cerebrospinal fluid. Bone marrow aspirate may demonstrate the characteristic haemophagocytes, but initially is non-diagnostic in two-thirds of patients. Established international clinical, haematological and biochemical criteria now facilitate accurate clinical diagnosis. The disease is fatal unless a haematopoietic stem cell transplant (HSCT) is performed. The introduction of HSCT has dramatically improved the prognosis of the disease. However, the mortality of the disease is still significantly high and a number of challenges remain to be addressed. Active disease at the time of the transplant is the major significant poor prognostic factor. Delayed diagnosis, after irreversible organ damage has occurred, especially neurological damage, disease reoccurrence and pre-transplant mortality, remain a concern.

Genotype-phenotype study of familial haemophagocytic lymphohistiocytosis type 3

BACKGROUND

Mutations of UNC13D are causative for familial haemophagocytic lymphohistiocytosis type 3 (FHL3; OMIM 608898).

OBJECTIVE

To carry out a genotype-phenotype study of patients with FHL3.

METHODS

A consortium of three countries pooled data on presenting features and mutations from individual patients with biallelic UNC13D mutations in a common database.

RESULTS

84 patients with FHL3 (median age 4.1 months) were reported from Florence, Italy (n=54), Hamburg, Germany (n=18), Stockholm, Sweden (n=12). Their ethnic origin was Caucasian (n=57), Turkish (n=10), Asian (n=7), Hispanic (n=4), African (n=3) (not reported (n=3)). Thrombocytopenia was present in 94%, splenomegaly in 96%, fever in 89%. The central nervous system (CNS) was involved in 49/81 (60%) patients versus 36% in patients with FHL2 (p=0.001). A combination of fever, splenomegaly, thrombocytopenia and hyperferritinaemia was present in 71%. CD107a expression, NK activity and Munc 13-4 protein expression were absent or reduced in all but one of the evaluated patients. 54 different mutations were observed, including 15 new ones: 19 missense, 14 deletions or insertions, 12 nonsense, nine splice errors. None was specific for ethnic groups. Patients with two disruptive mutations were younger than patients with two missense mutations (p<0.001), but older than comparable patients with FHL2 (p=0.001).

CONCLUSION

UNC13D mutations are scattered over the gene. Ethnic-specific mutations were not identified. CNS involvement is more common than in FHL2; in patients with FHL3 and disruptive mutations, age at diagnosis is significantly higher than in FHL2. The combination of fever, splenomegaly, thrombocytopenia and hyperferritinaemia appears to be the most easily and frequently recognised clinical pattern and their association with defective granule release assay may herald FHL3.

Subtypes of familial hemophagocytic lymphohistiocytosis in Japan based on genetic and functional analyses of cytotoxic T lymphocytes

Background

Familial hemophagocytic lymphohistiocytosis (FHL) is a rare disease of infancy or early childhood. To clarify the incidence and subtypes of FHL in Japan, we performed genetic and functional analyses of cytotoxic T lymphocytes (CTLs) in Japanese patients with FHL.

Design and Methods

Among the Japanese children with hemophagocytic lymphohistiocytosis (HLH) registered at our laboratory, those with more than one of the following findings were eligible for study entry under a diagnosis of FHL: positive for known genetic mutations, a family history of HLH, and impaired CTL-mediated cytotoxicity. Mutations of the newly identified causative gene for FHL5, STXBP2, and the cytotoxicity and degranulation activity of CTLs in FHL patients, were analyzed.

Results

Among 31 FHL patients who satisfied the above criteria, PRF1 mutation was detected in 17 (FHL2) and UNC13D mutation was in 10 (FHL3). In 2 other patients, 3 novel mutations of STXBP2 gene were confirmed (FHL5). Finally, the remaining 2 were classified as having FHL with unknown genetic mutations. In all FHL patients, CTL-mediated cytotoxicity was low or deficient, and degranulation activity was also low or absent except FHL2 patients. In 2 patients with unknown genetic mutations, the cytotoxicity and degranulation activity of CTLs appeared to be deficient in one patient and moderately impaired in the other.

Conclusions

FHL can be diagnosed and classified on the basis of CTL-mediated cytotoxicity, degranulation activity, and genetic analysis. Based on the data obtained from functional analysis of CTLs, other unknown gene(s) responsible for FHL remain to be identified.

Atypical familial hemophagocytic lymphohistiocytosis due to mutations in UNC13D and STXBP2 overlaps with primary immunodeficiency diseases

BACKGROUND

Familial hemophagocytic lymphohistiocytosis is a genetic disorder of lymphocyte cytotoxicity that usually presents in the first two years of life and has a poor prognosis unless treated by hematopoietic stem cell transplantation. Atypical courses with later onset and prolonged survival have been described, but no detailed analysis of immunological parameters associated with typical versus atypical forms of familial hemophagocytic lymphohistiocytosis has been performed.

DESIGN AND METHODS

We analyzed disease manifestations, NK-cell and T-cell cytotoxicity and degranulation, markers of T-cell activation and B-cell differentiation as well as Natural Killer T cells in 8 patients with atypical familial hemophagocytic lymphohistiocytosis due to mutations in UNC13D and STXBP2.

RESULTS

All but one patient with atypical familial hemophagocytic lymphohistiocytosis carried at least one splice-site mutation in UNC13D or STXBP2. In most patients episodes of hemophagocytic lymphohistiocytosis were preceded or followed by clinical features typically associated with immunodeficiency, such as chronic active Epstein Barr virus infection, increased susceptibility to bacterial infections, granulomatous lung or liver disease, encephalitis or lymphoma. Five of 8 patients had hypogammaglobulinemia and reduced memory B cells. Most patients had a predominance of activated CD8(+) T cells and low numbers of Natural Killer T cells. When compared to patients with typical familial hemophagocytic lymphohistiocytosis, NK-cell cytotoxicity and NK-cell and CTL degranulation were impaired to a similar extent. However, in patients with an atypical course NK-cell degranulation could be partially reconstituted by interleukin-2 and cytotoxic T-cell cytotoxicity in vitro was normal.

CONCLUSIONS

Clinical and immunological features of atypical familial hemophagocytic lymphohistiocytosis show an important overlap to primary immunodeficiency diseases (particularly common variable immunodeficiency and X-linked lymphoproliferative syndrome) and must, therefore, be considered in a variety of clinical presentations. We show that degranulation assays are helpful screening tests for the identification of such patients.

The outcome of hematopoietic stem cell transplantation in Korean children with hemophagocytic lymphohistiocytosis

Chemoimmunotherapy-based treatments have improved the survival of patients with HLH, but outcomes of the patients are still unsatisfactory. We report here the outcome of Korean children with HLH who underwent HSCT, which was analyzed from the data of a nation-wide HLH registry. Retrospective nation-wide data recruitment for the pediatric HLH patients diagnosed between 1996 and 2008 was carried out by the Histiocytosis Working Party of the Korean Society of Hematology. Nineteen patients who received HSCT among the total of 148 enrolled children with HLH were analyzed for the transplant-related variables and events. The probability of five-yr survival after HSCT was 73.3% with a median follow-up of 57. Two months compared to 54.3% for the patients who were treated with chemoimmunotherapy only (p = 0.05). The reasons for HSCT were active disease after eight wk of initial treatment (n = 9), relapsed disease (n = 5), and FHL (n = 5). Fourteen patients are currently alive without disease after HSCT, four patients died of treatment-related events (infection in two and graft failure in two) at early post-transplant period, and one patient died of relapse at one yr post transplantation. The survival of patients who were transplanted because of active disease after eight wk of initial treatment was worse compared to those patients who had inactive state at that time (60.6% vs. 100%, respectively, p = 0.06). Of the four patients who received transplants using cord blood, three died of graft failure (n = 2) and relapse (n = 1). The five-yr probability of survival after HSCT according to the donor type was 85.7% for the MRDs (n = 6), 87.5% for the MUDs (n = 8), and 40% for the MMUDs (n = 5) (p = 0.03). Other variables such as age, CNS involvement at the time of diagnosis, the etiology of HLH (familial or secondary), and the conditioning regimens had no influence on the five-yr OS of the HLH patients who underwent HSCT. HSCT improved the survival of the patients who had familial, relapsed, or severe and persistent SHLH in the Korean nation-wide HLH registry. Although numbers were small, these results are similar to other reports in the literature. The disease state after initial treatment, the stem cell source of the transplant, and the donor type were the important prognostic factors that affected the OS of the HLH patients who underwent HSCT.

Inherited defects in lymphocyte cytotoxic activity

The granule-dependent cytotoxic activity of lymphocytes plays a critical role in the defense against virally infected cells and tumor cells. The importance of this cytotoxic pathway in immune regulation is evidenced by the severe and often fatal condition, known as hemophagocytic lymphohistiocytic syndrome (HLH) that occurs in mice and humans with genetically determined impaired lymphocyte cytotoxic function. HLH manifests as the occurrence of uncontrolled activation of T lymphocytes and macrophages infiltrating multiple organs. In this review, we focus on recent advances in the characterization of effectors regulating the release of cytotoxic granules, and on the role of this cytotoxic pathway in lymphocyte homeostasis and immune surveillance. Analysis of the mechanisms leading to the occurrence of hemophagocytic syndrome designates gamma-interferon as an attractive therapeutic target to downregulate uncontrolled macrophage activation, which sustains clinical and biological features of HLH.

Perforin: structure, function, and role in human immunopathology

The secretory granule-mediated cell death pathway is the key mechanism for elimination of virus-infected and transformed target cells by cytotoxic lymphocytes. The formation of the immunological synapse between an effector and a target cell leads to exocytic trafficking of the secretory granules and the release of their contents, which include pro-apoptotic serine proteases, granzymes, and pore-forming perforin into the synapse. There, perforin polymerizes and forms a transmembrane pore that allows the delivery of granzymes into the cytosol, where they initiate various apoptotic death pathways. Unlike relatively redundant individual granzymes, functional perforin is absolutely essential for cytotoxic lymphocyte function and immune regulation in the host. Nevertheless, perforin is still the least studied and understood cytotoxic molecule in the immune system. In this review, we discuss the current state of affairs in the perforin field: the protein's structure and function as well as its role in immune-mediated diseases.

STX11 mutations and clinical phenotypes of familial hemophagocytic lymphohistiocytosis in North America

BACKGROUND

Mutations in STX11 are responsible for Familial Hemophagocytic Lymphohistiocytosis (FHLH) type 4, a rare primary immunodeficiency which has previously been observed only in patients of Kurdish, Turkish, and Lebanese ethnic background.

METHODS

We reviewed our experience with STX11 mutations among North American patients and studied the impact of patient mutations upon syntaxin 11 expression and NK cell function.

RESULTS

Between 2007 and 2008, 243 patients with HLH (lacking disease-causing mutations in PRF1 and UNC13D) were referred for STX11 mutational analysis. We observed 1 novel homozygous nonsense mutation, 73 G > T (E25X), occurring in Hispanic siblings, and 2 novel biallelic heterozygous missense mutations, 106G > C (E36Q) and 616G > A (E206K), occurring in 1 Caucasian patient. The N-terminal nonsense mutation resulted in absence of detectable syntaxin 11 and abrogation of in vitro NK cell degranulation and function, while the biallelic heterozygous missense mutations resulted in detectable mutated syntaxin 11 and preservation of in vitro NK cell degranulation and cytotoxicity. The two sibling patients with the nonsense mutations presented with HLH during infancy, whereas the patient with biallelic heterozygous missense mutations presented at 5 years of age.

CONCLUSION

We conclude that mutations in STX11 are responsible for HLH in approximately 1% of North American patients and can cause variable defects in syntaxin 11 expression and function with resultant impact on clinical phenotype.

Hematopoietic stem cell transplantation for familial hemophagocytic lymphohistiocytosis and Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis in Japan

BACKGROUND

Post-transplant outcomes of hemophagocytic lymphohistiocytosis (HLH) patients were analyzed in Japan where Epstein-Barr virus (EBV)-associated severe forms are problematic.

METHODS

Fifty-seven patients (43 familial HLH [12 FHL2, 11 FHL3, 20 undefined], 14 EBV-HLH) who underwent stem cell transplantation (SCT) between 1995 and 2005 were enrolled based on the nationwide registration.

RESULTS

Fifty-seven patients underwent 61 SCTs, including 4 consecutive SCTs. SCTs were employed using allogeneic donors in 93% of cases (allo 53, twin 1, auto 3). Unrelated donor cord blood transplantation (UCBT) was employed in half of cases (21 FHL, 7 EBV-HLH). Reduced intensity conditioning was used in 26% of cases. The 10-year overall survival rates (median +/- SE%) were 65.0 +/- 7.9% in FHL and 85.7 +/- 9.4% in EBV-HLH patients, respectively. The survival of UCBT recipients was >65% in both FHL and EBV-HLH patients. Three out of four patients were alive with successful engraftment after second UCBT. FHL patients showed a poorer outcome due to early treatment-related deaths (<100 days, seven patients) and a higher incidence of sequelae than EBV-HLH patients (P = 0.02). The risk of death for FHL patients having received an unrelated donor bone marrow transplant was marginally higher than that for a related donor SCT (P = 0.05) and that for UCBT (P = 0.07).

CONCLUSIONS

EBV-HLH patients had a better prognosis after SCT than FHL patients. FHL patients showed either an equal or better outcome even after UCBT compared with the recent reports. UCB might therefore be acceptable as an alternate SCT source for HLH patients, although the optimal conditioning remains to be determined.

UNC13D is the predominant causative gene with recurrent splicing mutations in Korean patients with familial hemophagocytic lymphohistiocytosis

BACKGROUND

Familial hemophagocytic lymphohistiocytosis is a fatal disease characterized by immune dysregulation from defective function of cytotoxic lymphocytes. Three causative genes have been identified for this autosomal recessive disorder (PRF1, UNC13D, and STX11). We investigated the molecular genetics of familial hemophagocytic lymphohistiocytosis in Korea.

DESIGN AND METHODS

Pediatric patients who fulfilled the HLH-2004 criteria were recruited from the Korean Registry for Histiocytosis. Molecular genetic studies were performed on the patients' DNA samples by direct sequencing of all coding exons and flanking sequences of PRF1, UNC13D, and STX11.

RESULTS

Forty patients were studied and familial hemophagocytic lymphohistiocytosis mutations were identified in nine; eight patients had UNC13D mutations (89%) and one had a mutation in PRF1. No patient had a STX11 mutation. Notably, four patients had only one UNC13D mutant allele, suggesting that the other mutation was missed by conventional direct sequencing. All UNC13D mutations were deleterious in nature. One known splicing mutation, c.754-1G>C, was recurrent, accounting for 58% of all the mutant alleles (7/12). Five UNC13D mutations were novel (p.Gln98X, p.Glu565SerfsX7, c.1993-2A>G, c.2367+1G>A, and c.2954+5G>A). The one patient with PRF1 mutation was homozygous for a frameshift mutation (p.Leu364GlufsX93), which was previously reported to be the most frequent PRF1 mutation in Japan.

CONCLUSIONS

This is the first investigation on the molecular genetics of familial hemophagocytic lymphohistiocytosis in Korea. The data showed that UNC13D is the predominant causative gene in the Korean population. The identification of mutations missed by conventional sequencing would better delineate the mutation spectrum and help to establish the optimal molecular diagnostic strategy for familial hemophagocytic lymphohistiocytosis in Korea, which might need an RNA-based screening strategy.

Comprehensive analyses and characterization of haemophagocytic lymphohistiocytosis in Vietnamese children

Haemophagocytic lymphohistiocytosis (HLH) is a fatal haematological disorder with diverse aetiology. This prospective study was undertaken to characterize HLH cases in Vietnamese children. Clinical and laboratory data, genetic analyses and outcome of the HLH patients were analysed. A total of 33 patients were enrolled from March 2007 to December 2008, with a median age of 3 years. Mutations of the SH2D1A (SAP) and PRF1 genes were detected in one patient, respectively. The virus association was high, up to 63.6% (21/33), including Epstein-Barr virus (19/33), cytomegalovirus (2/33) and dengue virus (2/33). Five patients had malignant lymphoma and two had autoimmune diseases. Twenty-eight patients were treated according to the HLH-2004 protocol. The first response rate was 64.3% (18/28), with an early death rate of 35.7% (10/28). High levels of interferon-gamma, interleukin-10, MIG and interferon-inducible protein-10 (IP-10) were associated with early mortality (P < 0.05). Reactivation among the responders was high (9/18) and the uneventful resolution was low (3/18) after a median follow-up of 35 weeks. In conclusion, the majority of HLH cases are associated with virus infections in Vietnamese children. Familial HLH is rare. The frequent reactivation and high mortality demands a more appropriate therapeutic regimen in tropical areas like Vietnam.

An unusual cause of multiple organ dysfunction syndrome in the pediatric intensive care unit: hemophagocytic lymphohistiocytosis

OBJECTIVE

To report our experience in children with primary or secondary hemophagocytic lymphohistiocytosis (HLH) presented with multiple organ dysfunction syndrome (MODS) in pediatric intensive care unit (PICU).

DESIGN

The records of patients with a diagnosis of HLH and MODS between January 2005 and January 2008 were reviewed. The patients' characteristics, treatment modalities, and outcomes were assessed.

SETTING

PICU of Ege University Hospital.

PATIENTS/SUBJECTS

Twelve children who were hospitalized in the PICU met the diagnostic criteria for HLH, and presented with MODS were entered into the study.

RESULTS

The median age of the patients was 3 years (range, 2 months-15.5 years). Six patients had a history of parental consanguinity and two had an affected sibling. Five of the patients were classified as primary HLH. All of the patients had hepatosplenomegaly, elevated ferritin levels, hypofibrinogenemia, anemia, thrombocytopenia, and hemophagocytosis in bone marrow examination at presentation. The median Pediatric Logistic Organ Dysfunction score of the patients at onset was 51 (range, 12-62). Four patients had six, four had five, two had four, and the remaining two had three organ dysfunctions. Organ dysfunction, other than hematologic dysfunction which was present in all patients, was most commonly seen in hepatic (n = 11, 91.7%), respiratory (n = 11, 91.7%), and cardiovascular systems (n = 10, 83.3%). Although nine patients showed neurologic dysfunction including convulsion and coma, renal failure was detected in five patients. Eleven patients were supported with mechanical ventilation and four patients required hemodialysis. Eight patients were treated according to the HLH 2004 treatment protocol, consisting of cyclosporine A, etoposide, and dexamethasone. The remaining four patients received only intravenous immunoglobulin and supportive treatment. Seven of the patients died.

CONCLUSION

HLH is a frequently lethal disease and with a clinical presentation similar to severe sepsis, MODS, disseminated intravascular coagulation, or septic shock, which are frequent diagnoses in the PICU. In the PICU, HLH should be considered in the case of prolonged fever, splenomegaly, cytopenia, and MODS. It is important for pediatricians and particularly pediatric intensivists to know the diagnostic criteria and possible clinical presentations of HLH so treatment is initiated promptly.

Highly elevated ferritin levels and the diagnosis of hemophagocytic lymphohistiocytosis

BACKGROUND

Hemophagocytic lymphohistiocytosis (HLH) is a potentially lethal condition characterized by a pathologic inflammation. The diagnostic criteria for HLH include fever, splenomegaly, cytopenias, hypertriglyceridemia, hypofibrinogenemia, abnormal natural killer cell (NK cell) functional assay, elevated soluble IL-2Ralpha level, and elevated ferritin level (>500 microg/L). Institution of timely therapy in these critically ill patients may be delayed by difficulties establishing the diagnosis. NK cell functional assay and soluble IL-2Ralpha level may require send-out to a specialized lab. However, ferritin level is available on a same-day basis at most institutions. In this study, we examined the utility of quantitative ferritin levels in diagnosing HLH.

PROCEDURE

All patients with ferritin values >500 microg/L obtained at Texas Children's Hospital between January 10, 2003 and January 10, 2005 were identified. Patient charts were reviewed for ferritin levels and hospital course.

RESULTS

During the study interval, 330 patients had ferritin levels >500 microg/L. Ten of the 330 patients were diagnosed with HLH. A ferritin level over 10,000 microg/L was 90% sensitive and 96% specific for HLH. Another diagnostic category with significantly elevated ferritin level was illness of unknown cause (n = 10), and only two of these patients were fully evaluated for HLH.

CONCLUSIONS

Ferritin levels above 10,000 microg/L appear to be specific and sensitive for HLH. In patients without a significant medical history and a new onset of febrile illness with highly elevated ferritin levels, the diagnosis of HLH should be evaluated.

Myelofibrosis in a patient with familial hemophagocytic lymphohistiocytosis

We report a unique case of primary hemophagocytic lymphohistiocytosis (HLH) detected in an infant who had bone marrow biopsies demonstrating myelofibrosis, a finding not previously reported in primary HLH.

Sequence analysis of the SRGN, AP3B1, ARF6, and SH2D1A genes in familial hemophagocytic lymphohistiocytosis

In the present study, DNA sequencing of the genes SRGN, ARF6, AP3B1, and SH2D1A was performed in a well defined cohort of 18 families with familial hemophagocytic lymphohistiocytosis (FHL). A heterozygous nucleotide change (C > T) in the 3'untranslated region of the SRGN gene and a monoallelic 3-base pair deletion (c.2409_2411delGAA) in exon 21 of the AP3B1 gene were observed in two different families. Additionally, two novel polymorphisms, one in intron 17 of AP3B1 and another in intron 2 of SH2D1A were identified. We conclude that mutations in SRGN, ARF6, and AP3B1 are not likely to be common in patients fulfilling the FHL criteria.

Fatal sibling cases of familial hemophagocytic lymphohistiocytosis (FHL) with MUNC13-4 mutations: case reports

The authors report here sibling cases of familial hemophagocytic lymphohistiocytosis (FHL) type 3 that took fatal courses despite intensive treatment. The older brother achieved remission by immunochemotherapy, but a central nervous system lesion occurred before the introduction of allogeneic hematopoietic stem cell transplantation (allo-HSCT). The patient died on day +1 of allo-HSCT due to progression of the disease. The younger brother developed symptoms of hemophagocytic lymphohistiocytosis mimicking neonatal hemochromatosis at birth. He died without a chance to receive allo-HSCT. Both siblings showed low natural killer cell (NK) activity and the compound heterozygous Munc13-4 gene mutations 1596+1 and 1723insA were identified postmortem in the younger brother. With recent progress in the molecular diagnosis of FHL, prompt and most appropriate therapeutic measures should be introduced to improve the prognosis of FHL patients.

Role of flow cytometry in the diagnosis and monitoring of primary immunodeficiency disease

This presentation is organized according to the recent classification of primary immunodeficiencies published by the International Union of Immunological Societies Primary Immunodeficiency meeting. The diseases have been classified into eight groups. After each list, individual diseases that are amenable to assessment by flow cytometry are reviewed with a brief clinical description and a discussion of the appropriate flow cytometry application.

Human natural killer cell deficiencies

PURPOSE OF REVIEW

Human natural killer cell deficiencies are a relevant clinical entity that provides insight into the role of natural killer cells in host defense, as well as the basic biology of natural killer cells. Since previously reviewing these disorders, significant developments warrant their reconsideration.

RECENT FINDINGS

Human natural killer cell deficiencies can occur as part of a more pervasive immunodeficiency syndrome or, rarely, in isolation. The most informative examples of the former are in the context of a known genetic defect, because the deficiency of natural killer cell development or activity can be attributed to the specific gene function. Since last reviewed, there are five human gene mutations that are now appreciated to affect natural killer cells, and additional new insights into natural killer cell biology have been obtained through seven others. Six new reports of isolated natural killer cell deficiencies, as well as a suggested classification scheme, are also reviewed.

SUMMARY

Appreciation of human genetic syndromes that include natural killer cell deficiencies, as well as new cases of isolated natural killer cell deficiencies, continue to advance the understanding of natural killer cell biology and solidify the role of natural killer cells in defense against human herpesviral infection.

Familial and acquired hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition of severe hyperinflammation caused by the uncontrolled proliferation of activated lymphocytes and histiocytes secreting high amounts of inflammatory cytokines. Cardinal signs and symptoms are prolonged fever, hepatosplenomegaly and pancytopenia. Characteristic biochemical markers include elevated triglycerides, ferritin and low fibrinogen. HLH occurs on the basis of various inherited or acquired immune deficiencies. Impaired function of natural killer (NK) cells and cytotoxic T-cells (CTL) is shared by all forms of HLH. Genetic HLH occurs in familial forms (FHLH) in which HLH is the primary and only manifestation, and in association with the immune deficiencies Chédiak-Higashi syndrome 1 (CHS 1), Griscelli syndrome 2 (GS 2) and x-linked lymphoproliferative syndrome (XLP), in which HLH is a sporadic event. Most patients with acquired HLH have no known underlying immune deficiency. Both acquired and genetic forms are triggered by infections, mostly viral, or other stimuli. HLH also occurs as a complication of rheumatic diseases (macrophage activation syndrome) and of malignancies. Several genetic defects causing FHLH have recently been discovered and have elucidated the pathophysiology of HLH. The immediate aim of therapy in genetic and acquired HLH is suppression of the severe hyperinflammation, which can be achieved with immunosuppressive/immunomodulatary agents and cytostatic drugs. Patients with genetic forms have to undergo stem cell transplantation to exchange the defective immune system with normally functioning immune effector cells. In conclusion, awareness of the clinical symptoms and of the diagnostic criteria of HLH is crucial in order not to overlook HLH and to start life-saving therapy in time.