Familial and acquired hemophagocytic lymphohistiocytosis

Exploration of a series of 5-arylidene-2-thioxoimidazolidin-4-ones as inhibitors of the cytolytic protein perforin

A series of novel 5-arylidene-2-thioxoimidazolidin-4-ones were investigated as inhibitors of the lymphocyte-expressed pore-forming protein perforin. Structure–activity relationships were explored through variation of an isoindolinone or 3,4-dihydroisoquinolinone subunit on a fixed 2-thioxoimidazolidin-4-one/thiophene core. The ability of the resulting compounds to inhibit the lytic activity of both isolated perforin protein and perforin delivered in situ by natural killer cells was determined. A number of compounds showed excellent activity at concentrations that were nontoxic to the killer cells, and several were a significant improvement on previous classes of inhibitors, being substantially more potent and soluble. Representative examples showed rapid and reversible binding to immobilized mouse perforin at low concentrations (≤2.5 μM) by surface plasmon resonance and prevented formation of perforin pores in target cells despite effective target cell engagement, as determined by calcium influx studies. Mouse PK studies of two analogues showed T_1/2 values of 1.1–1.2 h (dose of 5 mg/kg iv) and MTDs of 60–80 mg/kg (ip).

Interleukin-18 and IL-18 binding protein

Interleukin-18 (IL-18) is a member of the IL-1 family of cytokines. Similar to IL-1β, IL-18 is synthesized as an inactive precursor requiring processing by caspase-1 into an active cytokine but unlike IL-1β, the IL-18 precursor is constitutively present in nearly all cells in healthy humans and animals. The activity of IL-18 is balanced by the presence of a high affinity, naturally occurring IL-18 binding protein (IL-18BP). In humans, increased disease severity can be associated with an imbalance of IL-18 to IL-18BP such that the levels of free IL-18 are elevated in the circulation. Increasing number of studies have expanded the role of IL-18 in mediating inflammation in animal models of disease using the IL-18BP, IL-18-deficient mice, neutralization of IL-18, or deficiency in the IL-18 receptor alpha chain. A role for IL-18 has been implicated in several autoimmune diseases, myocardial function, emphysema, metabolic syndromes, psoriasis, inflammatory bowel disease, hemophagocytic syndromes, macrophage activation syndrome, sepsis, and acute kidney injury, although in some models of disease, IL-18 is protective. IL-18 plays a major role in the production of interferon-γ from T-cells and natural killer cells. The IL-18BP has been used safely in humans and clinical trials of IL-18BP as well as neutralizing anti-IL-18 antibodies are in clinical trials. This review updates the biology of IL-18 as well as its role in human disease.

A child with Epstein-Barr Virus-associated hemophagocytic lymphohistiocytosis complicated by coronary artery lesion mimicking Kawasaki disease

There is considerable overlap between hemophagocytic lymphohistiocytosis (HLH) and Kawasaki disease (KD) in terms of aberrant immune response though the etiology of KD remains unknown. We present a case fulfilling the criteria of both HLH and KD complicated by coronary artery dilatation: HLH was confirmed to be triggered by Epstein-Barr virus. This case alarms us the possibility that even patients with HLH may be complicated by coronary artery lesion, which is one of the hallmarks of KD. We would like to draw attention that if features of KD become apparent in patients with HLH, echocardiographic examinations should be performed not to miss coronary artery lesion.

Undiagnosed Chronic Granulomatous Disease, Burkholderia cepacia complex Pneumonia, and Acquired Hemophagocytic Lymphohistiocytosis: A Deadly Association

Background. Chronic granulomatous disease is a rare inherited disorder of the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. The clinical course of the disease is marked by recurrent infections, including Burkholderia cepacia complex infection. Case Report. Here we report the case of a 21-year-old male hospitalized for a Burkholderia cepacia complex pneumonia. Despite the broad spectrum antibiotic treatment, fever continued and patient's condition worsened. Anemia and thrombocytopenia developed together with hypofibrinogenemia. The patient died of multiple organ dysfunction 17 days after his admission. Autopsy revealed hemophagocytosis, suggesting the diagnosis of acquired hemophagocytic lymphohistiocytosis. DNA analysis showed a deletion in the p47phox gene, confirming the diagnosis of autosomal recessive chronic granulomatous disease. Discussion. In addition to chronic granulomatous disease, recent findings have demonstrated that Burkholderia cepacia complex can decrease activity of the NADPH oxidase. Interestingly, hemophagocytic lymphohistiocytosis is characterized by an impaired function of the T-cell mediated inflammation which is partly regulated by the NADPH oxidase. Physicians should therefore pay particular attention to this deadly association.

The hyperferritinemic syndrome: macrophage activation syndrome, Still's disease, septic shock and catastrophic antiphospholipid syndrome

BACKGROUND

Over the last few years, accumulating data have implicated a role for ferritin as a signaling molecule and direct mediator of the immune system. Hyperferritinemia is associated with a multitude of clinical conditions and with worse prognosis in critically ill patients.

DISCUSSION

There are four uncommon medical conditions characterized by high levels of ferritin, namely the macrophage activation syndrome (MAS), adult onset Still's disease (AOSD), catastrophic antiphospholipid syndrome (cAPS) and septic shock, that share a similar clinical and laboratory features, and also respond to similar treatments, suggesting a common pathogenic mechanism. Ferritin is known to be a pro-inflammatory mediator inducing expression of pro-inflammatory molecules, yet it has opposing actions as a pro-inflammatory and as an immunosuppressant. We propose that the exceptionally high ferritin levels observed in these uncommon clinical conditions are not just the product of the inflammation but rather may contribute to the development of a cytokine storm.

SUMMARY

Here we review and compare four clinical conditions and the role of ferritin as an immunomodulator. We would like to propose including these four conditions under a common syndrome entity termed "Hyperferritinemic Syndrome".

Haemophagocytic lymphohistiocytosis presenting as liver failure following Epstein-Barr and prior hepatitis A infections

Haemophagocytic lymphohistiocytosis (HLH) is associated with high mortality even after prompt diagnosis. We present a young man with HLH triggered by two common viral diseases, infectious mononucleosis and hepatitis A. This patient presented with fever, rapidly progressive liver failure, anasarca and cholestasis, followed by anaemia and neutropenia. His carbohydrate antigen 19-9 reached over 9000 U/mL. Initial bone marrow and liver biopsies did not show histological features of malignancy or HLH. The patient was finally diagnosed and treated almost 1 year after the initial symptoms started, and had an excellent response with etoposide and dexamethasone. This case is unusual because it was triggered following mononucleosis in a patient with positive total antibodies against hepatitis A, with rapidly developing liver failure, and also because the patient's response was excellent despite the delay in treatment. It underscores the importance of suspecting HLH when severe systemic illness develops after a viral infection, even in the absence of clear histological features.

Cytokine profiles in children with primary Epstein-Barr virus infection

Primary Epstein-Barr virus (EBV) infection causes infectious mononucleosis and hemophagocytic lymphohistiocytosis (HLH) in children, where EBV infects B and CD8(+) T cells, respectively. We measured pro-inflammatory and anti-inflammatory cytokines in both diseases. Significantly higher concentrations of various mediators, including interferon-γ, neopterin, interleukin (IL)-6, IL-10, IL-18, and heme oxygenase-1, were observed in EBV-HLH. Because of their similarity to the profile of familial HLH, this profile was likely a consequence of HLH, but not ectopic infection. TNF-α levels were elevated in both diseases. Elevation of those mediators may contribute to the disease pathogenesis of EBV-HLH by activating and inhibiting host immune responses.

Synaptobrevin2 is the v-SNARE required for cytotoxic T-lymphocyte lytic granule fusion

Cytotoxic T lymphocytes kill virus-infected and tumorigenic target cells through the release of perforin and granzymes via fusion of lytic granules at the contact site, the immunological synapse. It has been postulated that this fusion process is mediated by non-neuronal members of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex protein family. Here, using a synaptobrevin2-monomeric red fluorescence protein knock-in mouse we demonstrate that, surprisingly, the major neuronal v-SNARE synaptobrevin2 is expressed in cytotoxic T lymphocytes and exclusively localized on granzyme B-containing lytic granules. Cleavage of synaptobrevin2 by tetanus toxin or ablation of the synaptobrevin2 gene leads to a complete block of lytic granule exocytosis while leaving upstream events unaffected, identifying synaptobrevin2 as the v-SNARE responsible for the fusion of lytic granules at the immunological synapse.

Neonatal hemophagocytic lymphohistiocytosis associated with a vertical transmission of coxsackievirus B1

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome characterized by fever, cytopenias, hepatosplenomegaly, and coagulopathy with the background of hypercytokinemia. Early diagnosis and etoposide therapy are not established for affected newborns. An afebrile infant suffered from apnea 4 days after birth, showing leukocytosis, thrombocytopenia, coagulopathy, and cerebrospinal fluid pleocytosis. Serum levels of ferritin and sIL-2R were high. Bone marrow studies revealed activated/hemophagocytosing macrophages. Coxsackievirus B1 (CB1) was isolated from the throat and stool. Serum anti-CB1 antibody titers were elevated in the patient (4 → 16; 6 → 43 days after birth) and mother (128; 10 days after delivery). Normal expressions of perforin and CD107a precluded inherited HLH. The vertically transmitted CB1-HLH was successfully treated without administration of corticosteroid, cyclosporine, or etoposide. Serum cytokine levels showed dominant expression of monokines (IL-1β/6/8, and TNF-α) but not IFN-γ, which is the central player of inherited HLH. The cytokine profile might represent a unique pathophysiology of enterovirus-driven neonatal HLH.

Primary immunodeficiencies predisposed to Epstein-Barr virus-driven haematological diseases

Epstein-Barr virus (EBV), a ubiquitous human herpesvirus, maintains lifelong subclinical persistent infections in humans. In the circulation, EBV primarily infects the B cells, and protective immunity is mediated by EBV-specific cytotoxic T cells (CTLs) and natural killer (NK) cells. However, EBV has been linked to several devastating diseases, such as haemophagocytic lymphohistiocytosis (HLH) and lymphoproliferative diseases in the immunocompromised host. Some types of primary immunodeficiencies (PIDs) are characterized by the development of EBV-associated complications as their predominant clinical feature. The study of such genetic diseases presents an ideal opportunity for a better understanding of the biology of the immune responses against EBV. Here, we summarize the range of PIDs that are predisposed to EBV-associated haematological diseases, describing their clinical picture and pathogenetic mechanisms.

Hemophagocytic lymphohistiocytosis: an update on diagnosis and pathogenesis

Hemophagocytic lymphohistiocytosis (HLH) is a frequently fatal and likely underdiagnosed disease involving a final common pathway of hypercytokinemia, which can result in end-organ damage and death. Although an early diagnosis is crucial to decrease mortality, the definitive diagnosis is often challenging because of the lack of specificity of currently accepted diagnostic criteria and the absence of confirmatory gold standards. Because of the wide range of laboratory assays involved in the diagnosis of HLH, practicing pathologists from a broad spectrum of clinical specialties need to be aware of the disease so that they may appropriately flag results and convey them to their clinical counterparts. Our article summarizes these new advances in the diagnosis of HLH and includes a review of clinical findings, updated understanding of the pathogenesis, and promising new testing methods.

GDF15-mediated upregulation of ferroportin plays a key role in the development of hyperferritinemia in children with hemophagocytic lymphohistiocytosis

BACKGROUND

Growth differentiation factor 15 (GDF15), a divergent TGFβ superfamily, has recently been implicated in the modulation of iron homeostasis, acting as an upstream negative regulator of hepcidin, the key iron regulatory hormone produced primarily by hepatocytes. However, little is known about possible roles that GDF15 might play in the regulation of iron homeostasis and development of hyperferritinemia in children with hemophagocytic lymphohistiocytosis (HLH).

PROCEDURES

We compared serum GDF15 level and mRNA expressions of GDF15 and key molecules of iron metabolism, and made correlations between their expressions in children with HLH and control children.

RESULTS

Serum GDF15 level was remarkably higher in HLH group than that in controls, with median serum concentration of 1,700 and 260 pg/ml, respectively (P < 0.001). In addition, GDF15 mRNA was significantly upregulated but independent of hypoxia-inducible factor-mediated oxygen signaling pathway. More importantly, GDF15 induction was positively correlated to upregulation of ferroportin, the only cellular iron exporter, and to upregulation of ferritin heavy chain.

CONCLUSIONS

Our study suggests that GDF15 induction helps suppress further activation of macrophages in stressful physiologic states as HLH, and is intimately implicated in the development of hyperferritinemia by modulating the hepcidin-ferroportin axis, resulting in enhanced ferroportin-mediated iron efflux.

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.

Treatment of Epstein Barr virus-induced haemophagocytic lymphohistiocytosis with rituximab-containing chemo-immunotherapeutic regimens

Haemophagocytic lymphohistiocytosis (HLH) is a life threatening complication of Epstein-Barr virus (EBV) infection. The anti-CD20 antibody rituximab depletes B cells, leading to improved outcomes for patients with EBV-associated B-lymphoproliferative disorders. To gather data on the use of rituximab in EBV-HLH, we performed a retrospective investigation involving 42 EBV-HLH patients who had received treatment with rituximab-containing regimens. On average, patients received 3 rituximab infusions (range 1-10) at a median dose of 375 mg/m(2) . In all patients, rituximab was administered with other HLH-directed medications, including steroids, etoposide and/or ciclosporin. Rituximab-containing regimens appeared well tolerated and improved clinical status in 43% of patients. Examination of laboratory data obtained prior to and within 2-4 weeks after the first rituximab dose revealed significant reductions in EBV load (median load pre-rituximab: 114,200 copies/ml, median post-rituximab: 225 copies/ml, P = 0.0001) and serum ferritin levels (median ferritin pre-rituximab: 4260 μg/l, median post-rituximab: 1149 μg/l, P = 0.001). Thus, when combined with conventional HLH-directed therapies, rituximab improves symptoms, reduces viral load and diminishes inflammation. These data support the incorporation of rituximab into future prospective clinical trials for patients with EBV-HLH.

Chimeric antigen receptor-modified T cells for acute lymphoid leukemia

Chimeric antigen receptor-modified T cells with specificity for CD19 have shown promise in the treatment of chronic lymphocytic leukemia (CLL). It remains to be established whether chimeric antigen receptor T cells have clinical activity in acute lymphoblastic leukemia (ALL). Two children with relapsed and refractory pre-B-cell ALL received infusions of T cells transduced with anti-CD19 antibody and a T-cell signaling molecule (CTL019 chimeric antigen receptor T cells), at a dose of 1.4×10(6) to 1.2×10(7) CTL019 cells per kilogram of body weight. In both patients, CTL019 T cells expanded to a level that was more than 1000 times as high as the initial engraftment level, and the cells were identified in bone marrow. In addition, the chimeric antigen receptor T cells were observed in the cerebrospinal fluid (CSF), where they persisted at high levels for at least 6 months. Eight grade 3 or 4 adverse events were noted. The cytokine-release syndrome and B-cell aplasia developed in both patients. In one child, the cytokine-release syndrome was severe; cytokine blockade with etanercept and tocilizumab was effective in reversing the syndrome and did not prevent expansion of chimeric antigen receptor T cells or reduce antileukemic efficacy. Complete remission was observed in both patients and is ongoing in one patient at 11 months after treatment. The other patient had a relapse, with blast cells that no longer expressed CD19, approximately 2 months after treatment. Chimeric antigen receptor-modified T cells are capable of killing even aggressive, treatment-refractory acute leukemia cells in vivo. The emergence of tumor cells that no longer express the target indicates a need to target other molecules in addition to CD19 in some patients with ALL.

Pulmonary hypertension following haematopoietic stem cell transplantation for primary haemophagocytic lymphohistiocytosis

We report two children who developed severe, fatal pulmonary hypertension (PHT) after mismatched unrelated donor cord blood transplantation using reduced intensity conditioning for HLH. PHT was diagnosed on post mortem lung biopsies with no evidence of HLH, pulmonary veno-occlusive disease, infection or of idiopathic pulmonary hypertension. PHT may be an association with HLH and physicians treating HLH should be aware of this potential association.

X-linked agammaglobulinemia presenting with secondary hemophagocytic syndrome: a case report

Introduction. Coincidence of X-linked agammaglobulinemia (XLA) and secondary hemophagocytic syndrome (sHS) is atypical. Both diseases are rare and pathogenesis of the latter one is not clearly known. Case Presentation. A 5-year-old boy was diagnosed both with XLA and sHS. However, in his history, he did not have severe and recurrent infections. Bruton tyrosine kinase (BTK) gene mutation was present (c.1581_1584delTTTG). To the best of the authors' knowledge, coincidence of XLA and sHS had not been reported in the literature before. Conclusion. Patients with XLA are extremely vulnerable to recurrent bacterial infections. The diagnosis of XLA with sHS at any time of life is both an interesting and challenging situation without history of recurrent bacterial infections.

Debate around infection-dependent hemophagocytic syndrome in paediatrics

Background

Hemophagocytic syndrome (HPS) is clinically defined as a combination of fever, liver dysfunction, coagulation abnormalities, pancytopenia, progressive macrophage proliferation throughout the reticuloendothelial system, and cytokine over-production, and may be primary or secondary to infectious, auto-immune, and tumoral diseases. The most consistent association is with viral infections but, as it is still debated whether any micro-organisms are involved in its pathogenesis, we critically appraised the literature concerning HPS and its relationship with infections.

Discussion

Infection-dependent HPS has been widely observed, but there are no data concerning its incidence in children. A better understanding of the pathophysiology of HPS may clarify the interactions between the immune system and the variously implicated potential infectious agents. Epstein-Barr virus (EBV) infection has been prominently associated with HPS, with clonal proliferation and the hyperactivation of EBV-infected T cells. However, a number of other viral, bacterial, fungal, and parasitic infections have been reported in association with HPS. In the case of low-risk HPS, corticosteroids and/or intravenous immunoglobulin or cyclosporine A may be sufficient to control the biological process, but etoposide is recommended as a means of reversing infection-dependent lymphohistiocytic dysregulation in high-risk cases.

Summary

HPS is a potential complication of various infections. A polymerase chain reaction search for infectious agents including EBV, cytomegalovirus and Leishmania is recommended in clinical settings characterised by non-remitting fever, organomegaly, cytopenia and hyperferritinemia.

Hemophagocytic lymphohistiocytosis: pathogenesis and treatment

Hemophagocytic lymphohistiocytosis (HLH) is not an independent disease but rather a life-threatening clinical syndrome that occurs in many underlying conditions and in all age groups. HLH is the consequence of a severe, uncontrolled hyperinflammatory reaction that in most cases is triggered by an infectious agent. Persistent stimulation of lymphocytes and histiocytes results in hypercytokinemia, leading to the characteristic symptoms of HLH. Genetic defects in familial HLH and in immunodeficiency syndromes associated with albinism affect the transport, processing, and function of cytotoxic granules in natural killer cells and cytotoxic T lymphocytes. This leads to defective killing of target cells and a failure to contract the immune response. The defects are increasingly found also in adolescents and adults. Acquired HLH occurs in autoinflammatory and autoimmune diseases (macrophage activation syndrome) and in patients with iatrogenic immunosuppression or with malignancies, but also in otherwise healthy persons with infections. Treatment of HLH aims at suppressing hypercytokinemia and eliminating the activated and infected cells. In genetic HLH, hematopoietic stem cell transplantation (HSCT) is needed for the correction of the immune defect. Treatment modalities include immunosuppressive, immunomodulatory, and cytostatic drugs; T-cell antibodies; and anticytokine agents. Using immunochemotherapy, familial HLH, which had been invariably fatal, has become a curable disease with more than 50% survivors. Reduced intensity conditioning for HSCT, which is associated with less transplantation-related mortality, will further improve cure rates.

Central nervous system (CNS) involvement is a critical prognostic factor for hemophagocytic lymphohistiocytosis

Background

Hemophagocytic lymphohistiocytosis (HLH) is a rare multisystem disorder that frequently involves the central nervous system (CNS). We compared the clinical characteristics, treatment, and prognosis of patients with HLH according to the degree of CNS involvement.

Methods

The clinical manifestations, initial laboratory data, treatment, and outcomes for 50 patients diagnosed with HLH and treated at Asan Medical Center between January 1995 and August 2011 were retrospectively reviewed and analyzed. CNS involvement was defined as the presence of neurological symptoms or an elevated white blood cell (WBC) count in the cerebrospinal fluid (CSF).

Results

Among these 50 patients, 23 (46%) developed CNS disease. Among patients with CNS disease, 19 had neurological symptoms, including seizures, altered consciousness, facial palsy, dysarthria, and dysphagia. Four patients had elevated CSF WBC counts without neurological symptoms. Twelve patients had abnormal brain imaging results, including high signal intensity lesions on T2-weighted magnetic resonance imaging (MRI) findings, ventriculomegaly, hemorrhage, atrophy, and leptomeningeal enhancement. Patients with CNS disease had lower ferritin, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels as well as reduced 5-year survival as compared to those without CNS disease.

Conclusion

CNS involvement is common among patients with HLH. Overall, patients with CNS disease achieve poorer outcomes than patients without CNS involvement. To improve outcomes, physicians must carefully monitor the neurological manifestations in patients with HLH and administer the appropriate course of intensified chemotherapy to patients with CNS disease.

Haemophagocytic syndrome associated with mucormycosis infection

Several clinical forms of mucormycosis are recognized. The tendency of mucoraceous zygomycetes to invade the blood vessels often produces a disseminated infection. A case of disseminate mucormycosis complicated by a haemophagocytic syndrome (HS) in a 32-year-old Caucasian male is reported in this article. Few cases of infection-associated HS (IAHS), involving infections caused by fungi, have been reported. In all the recorded cases, the fungal infection coexists with malignant lymphoma, immunodeficiency and a long-term steroid therapy for renal transplant or Crohn's disease. This is the second described case of the HS due to mucormycosis.

Human herpesvirus 8-related Castleman disease in the absence of HIV infection

BACKGROUND

Castleman disease (CD) in the context of human immunodeficiency virus (HIV) infection is well described. It is almost always multicentric (MCD) and linked to human herpesvirus 8 (HHV-8). There are limited published data surrounding HHV-8-related CD among HIV-negative patients.

METHODS

From January 1995 through June 2012, we identified in a single center 18 HIV-seronegative patients with HHV-8-related CD. We report on their clinical, pathological, and laboratory features.

RESULTS

All cases were multicentric. Patients were aged 42-83 years and were referred with a relapsing remitting syndrome of fever (94%), constitutional symptoms (100%), peripheral lymphadenopathy (100%), splenomegaly (72%), hepatomegaly (50%), and edema (28%). Kaposi sarcoma was observed in 9 cases. Anemia and serum markers of inflammation were present in all cases. Polymerase chain reaction for HHV-8 DNA was positive on blood samples in all cases, whereas only 12 of 16 patients tested had positive HHV-8 serology at diagnosis. All cases showed the classic histological features of MCD, and LANA-1 immunostaining identified HHV-8-infected plasmablasts in 16 of 16 tested cases. Reactive hemophagocytic syndrome (44%), autoimmune hemolytic anemia (33%), and lymphoma (22%) were the commonest associated complications. Remission was obtained with etoposide in 13 of 15 cases. Rituximab allowed prolonged remission off therapy in 10 cases. Death occurred in 3 patients not treated with rituximab. These features were similar to those described in HIV-positive HHV-8-related MCD. Comparison between these 18 cases and 12 HIV-negative HHV-8-unrelated MCD cases showed marked discrepancies.

CONCLUSIONS

HHV-8-associated MCD may be considered as a single clinicopathological entity regardless of HIV status.

Diagnostic evaluation of patients with suspected haemophagocytic lymphohistiocytosis

Haemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome characterized by severely disturbed immune homeostasis. It can affect all age groups. Diagnostic evaluation of the patient with suspected HLH has to address three main questions: (i) does the patient have HLH? There is no simple diagnostic test, but a number of clinical and laboratory criteria define this clinical syndrome. (ii) Can a trigger be identified? A variety of infections, malignant or autoimmune diseases can contribute to the disturbed immune homeostasis with important consequences for treatment. (iii) Does the patient suffer from a genetic disease predisposing to HLH? Recent advances in the understanding of the genetic and pathophysiological basis of HLH have enabled a better and more rapid answer to this question, which is relevant for prognosis and the decision to perform haematopoietic stem cell transplantation. This review summarizes the current diagnostic approach to the patient with HLH.

Development of classical Hodgkin's lymphoma in an adult with biallelic STXBP2 mutations

Experimental model systems have delineated an important role for cytotoxic lymphocytes in the immunosurveillance of cancer. In humans, perforin-deficiency has been associated with occurrence of hematologic malignancies. Here, we describe an Epstein-Barr virus-positive classical Hodgkin's lymphoma in a patient harboring biallelic mutations in STXBP2, a gene required for exocytosis of perforin-containing lytic granules and associated with familial hemophagocytic lymphohistocytosis. Cytotoxic T lymphocytes were found infiltrating the tumor, and a high frequency of Epstein-Barr virus-specific cytotoxic T lymphocytes were detected in peripheral blood. However, lytic granule exocytosis and cytotoxicity by cytotoxic T lymphocytes, as well as natural killer cells, were severely impaired in the patient. Thus, the data suggest a link between defective lymphocyte exocytosis and development of lymphoma in STXBP2-deficient patients. Therefore, with regards to treatment of familial hemophagocytic lymphohistocytosis patients with mutations in genes required for lymphocyte exocytosis, it is important to consider both the risks of hemophagocytic lymphohistocytosis and malignancy.

Syntaxin-11, but not syntaxin-2 or syntaxin-4, is required for platelet secretion

The platelet release reaction plays a critical role in thrombosis and contributes to the events that follow hemostasis. Previous studies have shown that platelet secretion is mediated by Soluble NSF Attachment Protein Receptor (SNARE) proteins from granule and plasma membranes. The SNAREs form transmembrane complexes that mediate membrane fusion and granule cargo release. Although VAMP-8 (v-SNARE) and SNAP-23 (a t-SNARE class) are important for platelet secretion, the identity of the functional syntaxin (another t-SNARE class) has been controversial. Previous studies using anti-syntaxin Abs in permeabilized platelets have suggested roles for both syntaxin-2 and syntaxin-4. In the present study, we tested these conclusions using platelets from syntaxin-knockout mouse strains and from a Familial Hemophagocytic Lymphohistiocytosis type 4 (FHL4) patient. Platelets from syntaxin-2 and syntaxin-4 single- or double-knockout mice had no secretion defect. Platelets from a FHL4 patient deficient in syntaxin-11 had a robust defect in agonist-induced secretion although their morphology, activation, and cargo levels appeared normal. Semiquantitative Western blotting showed that syntaxin-11 is the more abundant syntaxin in both human and murine platelets. Coimmunoprecipitation experiments showed that syntaxin-11 can form SNARE complexes with both VAMP-8 and SNAP-23. The results of the present study indicate that syntaxin-11, but not syntaxin-2 or syntaxin-4, is required for platelet exocytosis.

Hemophagocytic lymphohistiocytosis complicated by central nervous system lesions in a patient with dermatomyositis: a case presentation and literature review

We report a case of dermatomyositis (DM) and hemophagocytic lymphohistiocytosis (HLH) complicated by central nervous system (CNS) lesions and review eight literature cases of DM and HLH. A 17-year-old woman, admitted to our hospital because of severe muscle weakness and high fever, was diagnosed with DM based on elevated serum levels of muscle enzymes and a typical skin rash. Pancytopenia, high serum ferritin and soluble interleukin (IL)-2 receptor, and hepatosplenomegaly were also noted. Bone-marrow examination was negative for hemophagocytosis. Steroid therapy combined with immunoglobulin i.v. was ineffective against the DM, pancytopenia, hepatic dysfunction, and hyperferritinemia. On the 27th hospital day, seizures and acute respiratory failure occurred. In the course of improving muscle enzyme levels after starting adjunctive treatment with cyclosporine, the patient suffered disturbed consciousness, dyskinesia, and tremor. Brain magnetic resonance imaging (MRI) revealed T2 hyperintense lesions in the pons. Additional cyclophosphamide pulse therapy successfully decreased serum ferritin. Unfortunately, the diffuse alveolar damage (DAD) confirmed by biopsy progressed and the patient died. Autopsy findings revealed DAD throughout both lungs, HLH liver lesions, and a hemorrhagic necrotic lesion of the pons in the brain. Even when pathological examination yields no findings of hemophagocytosis, it is important to comprehensively and rapidly diagnose HLH based on the clinical picture. Because DM complicated by HLH may be associated with abnormal production of cytokines and systemic autoimmune responses, it may be necessary to immediately administer additional immunosuppressive therapy. We describe and discuss the extraordinary, severe form of DM in our patient, along with cases in the literature.