Hyperinflammation, rather than hemophagocytosis, is the common link between macrophage activation syndrome and hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis secondary to visceral leishmaniasis: A case report of a rare complication of visceral leishmaniasis

Hemophagocytic lymphohistiocytosis (HLH) is a rare, potentially life-threatening clinical syndrome characterized by hyperactivation of inflammatory mediators and harmful end-organ damage. Visceral leishmaniasis (VL)-induced HLH is a rare disease with significant diagnostic and management implications. Herein, we present a case of secondary HLH as a complication of visceral leishmaniasis in a two-year-old toddler. A 2-year-old male toddler was admitted for evaluation of a prolonged 4-week fever. Accompanying the fever, he developed progressive abdominal swelling, intermittent bilateral nasal bleeding, and repeated chest-focus infections of similar duration. The patient was acutely sick, with chronic signs of malnutrition (mid-upper arm circumference of 10.5 cm), fever (39 °C), tachypnea (70 breaths/min), tachycardia (132 beats/min), pallor, and hepatosplenomegaly. Initial investigation revealed leukopenia (2240/μl), anemia (7.3 g/dl), and severe thrombocytopenia (26,000/μl). With consideration of febrile neutropenia, the patient was started on cefepime with further revision to vancomycin and meropenem based on the culture result. After 10 days of persistent fever and poor clinical condition, an immunochromatographic rapid test with the rK39 antigen was conducted, and the patient was found to be positive for Leishmania spp. Intravenous liposomal amphotericin B (AmBisome) was initiated. On the 6th day of treatment, the patient's clinical and laboratory profiles severely deteriorated, and further laboratory investigation showed elevated triglyceride (524 mg/dl) and ferritin levels (1500 ng/mL). VL-induced secondary HLH was confirmed, and intravenous dexamethasone was initiated. Subsequently, his clinical and laboratory findings significantly improved, and he was discharged with PO dexamethasone. Our case highlights the intricate nature of VL-induced HLH and the need for high index of suspicion and timely management.

Hemophagocytic lymphohistiocytosis after solid organ transplantation: A challenge for clinicians

Hemophagocytic lymphohistiocytosis (HLH) is a rare inflammatory disorder with a high mortality rate and a wide range of symptoms. Solid organ transplantation, which provides patients with a unique immunosuppressive state, is a less common predisposing factor for HLH. HLH after solid organ transplantation (HLH-SOT) is very rare and fatal. It is hard to diagnose and treat and extremely understudied. The use of immunosuppressants makes the situation of HLH-SOT more complex. This review summarizes the existing literature on HLH after solid organ transplantation and describes its triggers and symptoms, focusing on its diagnosis and treatment. We performed a literature search of case reports, case series, letters to the editor, and clinical quizzes describing patients with HLH after solid organ transplantation (HLH-SOT). We provide recommendations on the diagnosis protocol and treatment strategy based on the existing evidence.

Bacteria-Associated Cytokine Storm Syndrome

While viruses are considered the most common infectious triggers for cytokine storm syndromes (CSS), a growing list of bacterial pathogens, particularly intracellular organisms, have been frequently reported to be associated with this syndrome. Both familial and sporadic cases of CSS are often precipitated by acute infections. It is also important to note that an underlying precipitating infection might not be clinically obvious as the CSS clinical picture can mimic an infectious process or an overwhelming septicemia. It is important to detect such an underlying treatable condition. In addition, infections can also be acquired during the course of CSS due to the concurrent immune suppression with treatment. Optimal CSS outcomes require treating bacterial infections when recognized.CSS should always be suspected in patients presenting with a sepsis-like or multi-organ dysfunction picture. There are many criteria proposed to diagnose CSS in general, with HLH-2004 being the most commonly used. Alternatively, criteria have been proposed for CSS occurring in specific underlying conditions such as systemic lupus erythematosus (SLE) or systemic juvenile idiopathic arthritis (sJIA). However, waiting for many of these criteria to be fulfilled could lead to significant delay in diagnosis, and the physician needs a high index of suspicion for CSS in critically ill febrile hospitalized patients in order to properly recognize the condition. Thus, there should be diagnostic equipoise between CSS and infections, including bacterial, in this population. In this chapter, we discuss the more common bacterial precipitants of CSS with many of the cases being discussed in the pediatric age group.

Immune checkpoint inhibitor-associated hemophagocytic lymphohistiocytosis in a patient with chronic lymphocytic leukemia

Haemophagocytic lymphohistiocytosis (HLH) is a rare complication of immune checkpoint inhibitor therapy. A 55-year-old male with stable chronic lymphocytic leukemia presented with fevers and symptomatic anaemia after nine cycles of nivolumab for metastatic melanoma. Investigations were consistent with autoimmune haemolytic anemia and corticosteroids were initiated. Thrombocytopenia and elevated liver enzymes without evidence of chronic lymphocytic leukaemia transformation was present. Ferritin was elevated, and thus HLH was considered and subsequently confirmed on a bone marrow biopsy. Corticosteroid monotherapy was continued, with resolution of fevers and improvement in cytopenias and liver enzymes. A six month corticosteroid tapering regimen was initiated, and he remains in HLH remission. This case highlights the importance of prompt recognition of immune checkpoint inhibitor-related HLH in patients with concurrent haematological malignancy.

CXCL9 inhibition does not ameliorate disease in murine models of both primary and secondary hemophagocytic lymphohistiocytosis

Hemophagocytic Lymphohistiocytosis (HLH) is a group of disorders culminating in systemic inflammation and multi-organ failure with high incidence of hepatic dysfunction. Overproduction of IFN-γ is the main immunopathological driver in this disorder. Monokine induced by IFN-γ (CXCL9) serves as a biomarker for disease activity and response to treatment in this disorder. However, very little is understood about the actual functional role of CXCL9 in pathogenesis in HLH. In the current study, we sought to determine the role of CXCL9 in pathogenesis in murine models of both Familial HLH (prf1^-/-) and Toll Like Receptor (TLR) 9 repeated stimulation induced Macrophage Activation Syndrome (MAS), a form of secondary HLH. FHL and MAS were induced in both CXCL9 genetically deficient mice (cxcl9^-/-) and controls as well as using AMG487, a pharmacological antagonist of the CXCL9 receptor, CXCR3. Results showed that CXCL9 genetic deficiency did not improve disease parameters or hepatitis in both models. Consistent with genetic ablation of CXCL9, inhibition of its receptor, CXCR3, by AMG487 did not show any significant effects in the FHL model. Taken together, inhibition of CXCL9-CXCR3 interaction does not ameliorate HLH physiology in general, or hepatitis as a classical target organ of disease.

Clinical value of soluble fms-like tyrosine kinase 1 (sFlt-1) in adult secondary hemophagocytic lymphohistiocytosis

BACKGROUND

Secondary hemophagocytic lymphohistiocytosis (sHLH) is a syndrome characterized by an excessive systemic inflammatory response, manifested by multiple organ dysfunction, lacking reliable immune biomarkers for predicting their inflammatory status and prognosis. Soluble fms-like tyrosine kinase 1 (sFlt-1) is associated with various inflammation-related diseases, including sepsis and severe organ failure.

METHODS

This study retrospectively included 32 adult sHLH patients diagnosed from January 2020 to December 2021. The expression of Flt-1 in peripheral blood CD14 + monocytes was detected by flow cytometry, and the level of plasma sFlt-1 was detected by ELISA.

RESULTS

In our study, the results of flow cytometry reveal that the Flt-1 expression on CD14 + monocytes of peripheral blood from sHLH patients was higher than that in normal control. In plasma samples of sHLH patients, sFlt-1 levels were 677.8 (463.2-929.7) pg/mL, significantly higher than in normal controls 377.18 (350.4-424.6) pg/mL and sepsis group 378.3 (257.0-499.1) pg/mL. Besides, a positive correlation was found between sFlt-1 and IL-6 in sHLH patients. The analysis of univariate Cox regression indicated that sFlt-1 >681.5 pg/mL demonstrated unfavorable overall survival ( p = 0.022). Multivariate analysis demonstrated that sFlt-1 >681.5 pg/mL was an independent factor associated with OS ( p = 0.041) after adjustment for confounders. Restricted cubic spline confirmed a linear and positive association between sFlt-1 and mortality risk.

CONCLUSION

Retrospective analysis showed that sFlt-1 was a promising prognostic factor.

Bone marrow alterations in COVID-19 infection: The root of hematological problems

INTRODUCTION

The 2019 coronavirus disease (COVID-19) is a respiratory infection caused by the SARS-CoV-2 virus with a significant impact on the hematopoietic system and homeostasis. The effect of the virus on blood cells indicates the involvement of the bone marrow (BM) as the place of production and maturation of these cells by the virus and it reminds the necessity of investigating the effect of the virus on the bone marrow.

METHOD

To investigate the effects of COVID-19 infection in BM, we reviewed literature from the Google Scholar search engine and PubMed database up to 2022 using the terms "COVID-19; SARS-CoV-2; Bone marrow; Thrombocytopenia; Hemophagocytosis; Pancytopenia and Thrombocytopenia.

RESULTS

Infection with the SARS-CoV-2 virus is accompanied by alterations such as single-line cytopenia, pancytopenia, hemophagocytosis, and BM necrosis. The presence of factors such as cytokine release syndrome, the direct effect of the virus on cells through different receptors, and the side effects of current treatments such as corticosteroids are some of the important mechanisms in the occurrence of these alterations.

CONCLUSION

To our knowledge, this review is the first study to comprehensively investigate BM alterations caused by SAR-CoV-2 virus infection. The available findings show that the significant impact of this viral infection on blood cells and the clinical consequences resulting from them are deeper than previously thought and it may be rooted in the changes that the virus causes in the BM of patients.

Specific cytokine patterns in Epstein-Barr virusassociated hemophagocytic lymphohistiocytosis compared to Kawasaki disease in children

The aim of the study was to test whether the cytokine profile could be used as a marker to differentiate between Epstein-Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and Kawasaki disease (KD). A total of 70 hospitalized children with HLH and KD admitted to hospital for the first time from March 2017 to December 2021 were enrolled in this study. Fifty-five healthy children were enrolled as normal controls. All patients and normal controls were tested for the six cytokines including interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), and interferon-γ (IFN-γ) by flow cytometry. IL-10 and IFN-γ levels were significantly higher in children with EBV-HLH than in the KD, IL-6 was lower in EBV-HLH patients than in the KD. IL-10/IL-6 ratio, IFN-γ/IL-6 ratio and IL10/IFN-γ ratio in children with EBV-HLH were significantly much higher than children in the KD group. When the diagnostic cutoff values of IL-10, IFN-γ, IL-10/IL-6 ratio and IFN-γ/IL-6 ratio were >13.2 pg/ml, >71.0 pg/ml, >0.37 and >1.34, respectively, the sensitivity and specificity of the diagnosis of EBV-HLH disease were 91.7% and 97.1%, 72.2% and 97.1%, 86.1% and 100.0%, and 75.0% and 97.1%, respectively. Notably high IL-10 and IFN-γ and moderately elevated IL-6 suggest the diagnosis of EBV-HLH, while high IL-6 levels with low IL-10 or IFN-γ concentration would suggest KD. Additionally, IL-10/IL-6 ratio or IFN-γ/IL-6 ratio could be used as an index to differentiate between EBV-HLH and KD.

Hemophagocytic Lymphohistiocytosis Following COVID-19 Infection

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been associated with multiple inflammatory symptoms involving several organ systems, including hematologic manifestations. Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome caused by excessive inflammation in the absence of immune regulation. We present the case of a patient with HLH secondary to dysregulated inflammatory response following COVID-19; we also describe the diagnostic and management challenges associated with the condition.

Cytokine profile, ferritin and multi-visceral involvement characterize macrophage activation syndrome during adult-onset Still's disease

OBJECTIVES

To multidimensionally characterize macrophage activation syndrome (MAS) complicating adult-onset Still's disease (AOSD) considering cytokine profile, inflammatory markers and multi-visceral involvement of the disease. To perform a high-dimensional phenotypic analysis of circulating immune cells in AOSD patients with and without MAS. To assess interferon (IFN)-related pathways in AOSD synovial tissues by a bulky RNA sequencing.

METHODS

Clinical and biologic data were collected and compared in AOSD patients with and without MAS. Sera biomolecules were analysed by Luminex multiplexing technology. Mass cytometry (CyTOF) was used to characterize circulating immune cells. A bulky RNA sequencing was performed in AOSD synovial tissues.

RESULTS

Forty consecutive AOSD patients were assessed, 14 complicated with MAS. Paralleling with increases of systemic score and ferritin, MAS patients showed higher levels of IL-1α, IL-1β, IL-1Ra, IL-2Ra, IL-6, IL-10, IL-17A, IFN-γ, G-CSF, MCP-1, MIP-1α and SCF. Combining the discriminatory ability of these data in identifying MAS, the best model was composed by systemic score, ferritin, IFN-γ and IL-10. By CyTOF analysis, MAS patients showed an increase of circulating 'classical monocytes' and a reduction of total NK cells. Our assessment showed 3477 IFN-related genes (IRGs) were differently expressed in AOSD synovial tissues.

CONCLUSIONS

A multidimensional characterization of AOSD patients suggested that IFN-γ, IL-10, ferritin and systemic score discriminated the occurrence of cytokine storm syndrome associated with MAS. The inflammatory milieu of AOSD and MAS may be related to a signature of circulating immune cells. Finally, our results about IRGs reinforced the role of IFN-γ in these patients.

The Role of Immune Mechanisms, Inflammatory Pathways, and Macrophage Activation Syndrome in the Pathogenesis of Hemophagocytic Lymphohistiocytosis

This review article describes the pathophysiology of hemophagocytic lymphohistiocytosis (HLH). The condition is characterized by excessive stimulation of inflammatory cytokines, lymphocytes, and macrophages, leading to hyperinflammatory disorder with immune dysfunction. The main clinical and diagnostic features include fever ≥38.5°C, splenomegaly, hyperferritinemia, cytopenia, hypofibrinogenemia, hemophagocytosis on the bone marrow, low or absent of natural killer (NK) cell activity, and elevated soluble CD25. Various immunological and inflammatory mechanisms are involved in the pathogenesis of HLH. Moreover, the condition can result in multisystem organ failure, contributing to the high mortality rate in hospital settings. A thorough literature search was conducted by collecting data from multiple articles published on PubMed, Medline, and Google Scholar. The article discusses the cellular and molecular pathways that lead to HLH. Due to the high rate of morbidity and mortality, early diagnosis needs to be established. More research pertaining to molecular biology, immunology, and the genetics of HLH is needed to explore the effective management and treatment of this rare disorder.

Excessive IL-10 and IL-18 trigger hemophagocytic lymphohistiocytosis-like hyperinflammation and enhanced myelopoiesis

BACKGROUND

Hyperinflammation is a life-threatening condition associated with various clinical disorders characterized by excessive immune activation and tissue damage. Multiple cytokines promote the development of hyperinflammation; however, the contribution of IL-10 remains unclear despite emerging speculations for a pathological role. Clinical observations from hemophagocytic lymphohistiocytosis (HLH), a prototypical hyperinflammatory disease, suggest that IL-18 and IL-10 may collectively promote the onset of a hyperinflammatory state.

OBJECTIVE

We aimed to investigate the collaborative roles of IL-10 and IL-18 in hyperinflammation.

METHODS

A comprehensive plasma cytokine profile for 87 secondary HLH patients was first depicted and analyzed. We then investigated the systemic and cellular effects of coelevated IL-10 and IL-18 in a transgenic mouse model and cultured macrophages. Single-cell RNA sequencing was performed on the monocytes/macrophages isolated from secondary HLH patients to explore the clinical relevance of IL-10/IL-18-mediated cellular signatures. The therapeutic efficacy of IL-10 blockade was tested in HLH mouse models.

RESULTS

Excessive circulating IL-10 and IL-18 triggered a lethal hyperinflammatory disease recapitulating HLH-like phenotypes in mice, driving peripheral lymphopenia and a striking shift toward enhanced myelopoiesis in the bone marrow. IL-10 and IL-18 polarized cultured macrophages to a distinct proinflammatory state with pronounced expression of myeloid cell-recruiting chemokines. Transcriptional characterization suggested the IL-10/IL-18-mediated cellular features were clinically relevant with HLH, showing enhanced granzyme expression and proteasome activation in macrophages. IL-10 blockade protected against the lethal disease in HLH mouse models.

CONCLUSION

Coelevated IL-10 and IL-18 are sufficient to drive HLH-like hyperinflammatory syndrome, and blocking IL-10 is protective in HLH models.

The hyper-expression of NLRP4 characterizes the occurrence of macrophage activation syndrome assessing STING pathway in adult-onset Still's disease

To assess stimulator of interferon genes (STING) pathway in patients with adult-onset Still's disease (AOSD) who were complicated or not by macrophage activation syndrome (MAS), evaluating peripheral blood mononuclear cells (PBMCs), and synovial tissues. The relative mRNA expression of key molecules of the STING pathway (i.e. CGAS, NLRP4, PKDC, STING1, XRCC5, and XRCC6) and interferon (IFN)-γ was assessed in PBMCs obtained from patients with AOSD, who were complicated or not by MAS, and healthy controls (HCs). A bulky RNA sequencing was performed in synovial tissues from two patients with AOSD. Finally, the ability of heavy ferritin subunit (FeH) to induce the expression of NLRP4 was evaluated in cultured macrophages. Twenty patients with AOSD were analysed. Out of them, seven patients were complicated by MAS. Assessing mRNA relative expression in PBMCs, STING1, NLRP4, XRCC6, and IFN-γ were significantly expressed in AOSD than HCs. The mRNA relative expression of CGAS, PKDC, and XRCC5 did not differ between patients and HCs. Furthermore, NLRP4 and IFN-γ resulted to be significantly increased in patients with AOSD complicated by MAS than others. By RNA-sequencing analysis, we observed that Nlrp4 gene was significantly up-regulated in patients with AOSD. Following the stimulation with FeH, an increased expression of NLRP4 was observed in cultured macrophages. In conclusion, an increased expression of some key molecules of STING pathway characterized patients with AOSD. In addition, our results suggested that a hyper-activity of NLRP4 may be observed in patients with MAS. Furthermore, FeH increased the expression of NLRP4 in cultured macrophages.

Infection-Triggered Hyperinflammatory Syndromes in Children

An association between infectious diseases and macrophage activation syndrome (MAS) has been reported, yet the exact role of infection in MAS development is still unclear. Here, a retrospective analysis of the clinical records of patients with rheumatic diseases complicated with MAS who were treated in a pediatric tertiary care center between 2011 and 2020 was performed. Any infection documented within the 30 days preceding the onset of MAS was reported. Out of 125 children in follow-up for systemic rheumatic diseases, 12 developed MAS, with a total of 14 episodes. One patient experienced three episodes of MAS. Clinical and/or laboratory evidence of infection preceded the onset of MAS in 12 events. Clinical features, therapeutic strategies, and patient outcomes were described. The aim of this study was to evaluate the possible role of infection as a relevant trigger for MAS development in children with rheumatic conditions. The pathogenetic pathways involved in the cross-talk between uncontrolled inflammatory activity and the immune response to infection deserve further investigation.

Characteristics and prognostic value of pleural effusion in secondary hemophagocytic lymphohistiocytosis

The clinical features of patients with secondary hemophagocytic lymphohistiocytosis (sHLH) complicated with pleural effusion have rarely been evaluated. We retrospectively analyzed 203 patients newly diagnosed with sHLH from July 2015 to July 2019 according to the HLH-2004 protocol. Baseline characteristics, laboratory results, and imaging were reviewed. Pleural effusion was found in 58.6% of the studied sHLH population, and characteristic imaging findings were minimal volume and bilaterality. Patients with pleural effusion had lower PLT counts, HB levels and ALB levels as well as higher sCD25 levels than those without pleural effusion (all p values < 0.05). Multivariate analyses showed that lg(sCD25) and PLT ≤ 65 × 10⁹/L were significant risk factors for developing pleural effusion in sHLH. Regarding prognostic value, survival analysis showed a lower survival probability for patients with pleural effusion than for those without pleural effusion (median OS, 90 vs. 164 days, p = 0.028). In multivariate analysis, pleural effusion was an independent prognostic factor for overall survival (OS) (HR 2.68; 95% CI 1.18–6.11, p = 0.019). Pleural effusion is frequently found in patients with sHLH and is associated with greater inflammation and worse outcomes.

Clinical aspects and presumed etiology of multisystem inflammatory syndrome in children (MIS-C): A review

The COVID-19 outbreak sparked by SARS-CoV-2, begat significant rates of malady worldwide, where children with an abnormal post-COVID ailment called the Multisystem Inflammatory Syndrome (MIS-C), were reported by April 2020. Here we have reviewed the clinical characteristics of the pediatric patients and the prognosis currently being utilized. A vivid comparison of MIS-C with other clinical conditions has been done. We have addressed the probable etiology and fundamental machinery of the inflammatory reactions, which drive organ failure. The involvement of androgen receptors portrays the likelihood of asymptomatic illness in children below adolescence, contributing to the concept of antibody-dependent enhancement.

Hemophagocytic Lymphohistiocytosis

CONTEXT.—

Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening disorder of immune regulation that can eventually result in end-organ damage and death. HLH is characterized by uncontrolled activation of cytotoxic T lymphocytes, natural killer cells, and macrophages that can lead to a cytokine storm. The diagnosis of HLH is often challenging due to the diverse clinical manifestations and the presence of several diagnostic mimics. The prognosis is generally poor, warranting rapid diagnosis and aggressive management.

OBJECTIVE.—

To provide a comprehensive review of the pathogenesis, clinical features, diagnosis, and management of HLH.

DATA SOURCES.—

Peer-reviewed literature.

CONCLUSIONS.—

HLH is a condition where a complete understanding of the pathogenesis, early diagnosis, and proper management has an important role in determining patient outcome. Genetic mutations causing impairment in the function of cytotoxic T lymphocytes and natural killer cells have been identified as the root cause of familial HLH; however, the specific pathogenesis of acquired HLH is unclear. The HLH-2004 protocol used in the diagnosis of HLH was originally developed for the pediatric population. The HLH-2004 protocol still forms the basis of the diagnosis of HLH in adults, although its use in adults has not been formally validated yet. Treatment of HLH is primarily based on the HLH-94 protocol, which involves suppressing the inflammatory response, but the treatment needs to be modified in adults depending on the underlying cause and comorbidities.

Definition and validation of serum biomarkers for optimal differentiation of hyperferritinaemic cytokine storm conditions in children: a retrospective cohort study

BACKGROUND

Cytokine storm syndromes are life-threatening complications that can occur in children with rheumatic conditions (macrophage activation syndrome [MAS]), inherited cytotoxicity defects (ie, primary haemophagocytic lymphohistiocytosis [HLH]), or as a result of infection or malignancies (ie, secondary HLH). To adequately steer treatment, an early and clear discrimination of these entities is essential. We aimed to define and validate serum biomarker profiles that can differentiate between primary HLH, secondary HLH (predominantly infection-associated), and MAS associated with systemic juvenile idiopathic arthritis (systemic JIA-MAS).

METHODS

In this multicentre, retrospective, cohort study, serum samples from patients (0-18 years) with a clinical diagnosis of primary HLH, secondary HLH, or systemic JIA-MAS were analysed by immunoassays for 55 cytokines and chemokines. Serum samples were collected from patients treated at seven clinical centres in Europe and North America. 15 serum biomarkers were validated using an independent commercial assay, and the diagnostic accuracy of the best performing biomarkers was tested in an independent validation cohort.

FINDINGS

Serum samples were collected between Dec 7, 2010, and Jan 26, 2018. In the discovery cohort of 43 patients (24 girls and 19 boys) multi-marker analyses revealed distinct serum biomarker profiles associated with primary or secondary HLH versus systemic JIA-MAS. Ten biomarkers were identified that were differentially elevated in either HLH or systemic JIA-MAS and distinguished between these clinical entities, six of which were tested in an independent validation cohort of 79 patients (34 girls and 45 boys). Serum concentrations of S100A12 and interleukin-18, as well as ratios of both S100A12 and IL-18 with chemokine (C-X-C motif) ligand (CXCL)9 and CXCL10 were identified as the most promising candidates for differential diagnostics.

INTERPRETATION

At initial presentation, when it is unclear whether a patient with excessive hyperferritinaemic inflammation has primary HLH, infection-associated secondary HLH, or MAS, high serum concentrations of S100A12 indicate an initial differential diagnosis of systemic JIA-MAS, thus helping to guide subsequent treatment decisions. We therefore suggest the inclusion of serum S100A12 and IL-18 in the diagnostic investigations for hyperferritinaemic syndromes; however, the definition and introduction of universially applicable cutoff values are still required.

FUNDING

German Research Foundation, the Center for Interdisciplinary Clinical Research at University Hospital Muenster, the EU's Horizon 2020 research and innovation programme, and the Deutsche Kinderkrebsstiftung.

Problems of Pathogenesis and Pathogenetic Therapy of COVID-19 from the Perspective of the General Theory of Pathological Systems (General Pathological Processes)

The COVID-19 pandemic examines not only the state of actual health care but also the state of fundamental medicine in various countries. Pro-inflammatory processes extend far beyond the classical concepts of inflammation. They manifest themselves in a variety of ways, beginning with extreme physiology, then allostasis at low-grade inflammation, and finally the shockogenic phenomenon of "inflammatory systemic microcirculation". The pathogenetic core of critical situations, including COVID-19, is this phenomenon. Microcirculatory abnormalities, on the other hand, lie at the heart of a specific type of general pathological process known as systemic inflammation (SI). Systemic inflammatory response, cytokine release, cytokine storm, and thrombo-inflammatory syndrome are all terms that refer to different aspects of SI. As a result, the metabolic syndrome model does not adequately reflect the pathophysiology of persistent low-grade systemic inflammation (ChSLGI). Diseases associated with ChSLGI, on the other hand, are risk factors for a severe COVID-19 course. The review examines the role of hypoxia, metabolic dysfunction, scavenger receptors, and pattern-recognition receptors, as well as the processes of the hemophagocytic syndrome, in the systemic alteration and development of SI in COVID-19.

Updating the NLRC4 Inflammasome: from Bacterial Infections to Autoimmunity and Cancer

Inflammasomes comprise a family of cytosolic multi-protein complexes that modulate the activation of cysteine-aspartate-specific protease 1 (caspase-1) and promote the maturation and secretion of interleukin (IL)-1β and IL-18, leading to an inflammatory response. Different types of inflammasomes are defined by their sensor protein which recognizes pathogenic ligands and then directs inflammasome assembly. Although the specific molecular mechanisms underlying the activation of most inflammasomes are still unclear, NLRC4 inflammasomes have emerged as multifaceted agents of the innate immune response, playing important roles in immune defense against a variety of pathogens. Other studies have also expanded the scope of NLRC4 inflammasomes to include a range of inherited human autoimmune diseases as well as proposed roles in cancer. In this review article, we provide an updated overview of NLRC4 inflammasomes, describing their composition, activation mechanisms and roles in both microbial infections and other disease conditions.

The joint involvement in adult onset Still's disease is characterised by a peculiar magnetic resonance imaging and a specific transcriptomic profile

Adult onset Still's disease (AOSD) is a rare systemic autoinflammatory disease, characterised by fever, arthritis, and skin rash, and joint involvement is one of its clinical manifestations. The aims of this work were to assess joint involvement, to describe main patterns of involvement, and associated clinical characteristics. In this work, we aimed at assessing the joint involvement in AOSD by using MRI, to describe main patterns and associated clinical characteristics. In addition, we aimed at assessing the global transcriptomic profile of synovial tissues in AOSD to elucidate possible pathogenic pathways involved. We also evaluated the global transcriptomic profile of synovial tissues to elucidate possible pathogenic pathways involved in the disease. Thus, AOSD patients, who underwent to MRI exam on joints, were assessed to describe patterns of joint involvement and associated clinical characteristics. Some synovial tissues were collected for RNA-sequencing purposes. The most common MRI finding was the presence of synovitis on 60.5%, mainly in peripheral affected joints, with low to intermediate signal intensity on T1-weighted images and intermediate to high signal intensity on T2-fat-saturated weighted and STIR images. Bone oedema and MRI-bone erosions were reported on 34.9% and 25.6% MRI exams, respectively. Patients with MRI-bone erosions showed a higher prevalence of splenomegaly, a more frequent chronic disease course, lower levels of erythrocyte sedimentation rate, and ferritin. In AOSD synovial tissues, a hyper-expression of interleukin (IL)-1, IL-6, and TNF pathways was shown together with ferritin genes. In conclusion, in AOSD patients, the most common MRI-finding was the presence of synovitis, characterised by intermediate to high signal intensity on T2-fat-saturated weighted and STIR images. MRI-bone erosions and bone oedema were also observed. In AOSD synovial tissues, IL-1, IL-6, and TNF pathways together with ferritin genes resulted to be hyper-expressed.

Line-selective macrophage activation with an anti-CD40 antibody drives a hemophagocytic syndrome in mice

Hemophagocytic syndromes comprise a cluster of hyperinflammatory disorders, including hemophagocytic lymphohistiocytosis and macrophage activation syndrome. Overwhelming macrophage activation has long been considered a final common pathway in the pathophysiology of hemophagocytic syndromes leading to the characteristic cytokine storm, laboratory abnormalities, and organ injuries that define the clinical spectrum of the disease. So far, it is unknown whether primary macrophage activation alone can induce the disease phenotype. In this study, we established a novel mouse model of a hemophagocytic syndrome by treating mice with an agonistic anti-CD40 antibody (Ab). The response in wild-type mice is characterized by a cytokine storm, associated with hyperferritinemia, high soluble CD25, erythrophagocytosis, secondary endothelial activation with multiple organ vaso-occlusion, necrotizing hepatitis, and variable cytopenias. The disease is dependent on a tumor necrosis factor-α-interferon-γ-driven amplification loop. After macrophage depletion with clodronate liposomes or in mice with a macrophage-selective deletion of the CD40 gene (CD40flox/flox/LysMCre), the disease was abolished. These data provide a new preclinical model of a hemophagocytic syndrome and reinforce the key pathophysiological role of macrophages.

Epstein-Barr virus induced haemophagocytic lymphohistiocytosis

Haemophagocytic lymphohistiocytosis (HLH) is a rare condition of uncontrolled immune activation as a result of an inherited genetic defect or in response to malignancy, autoimmune disease, rheumatological disease, AIDS infection or post-transplant immunosuppression. Described here is the case of a 19-year-old Caucasian man who presented with complaints of worsening fever, new-onset jaundice and lethargy after failing treatment for suspected infectious mononucleosis. Physical examination was significant for fever and splenomegaly while laboratory results revealed transaminitis, cytopaenia, indirect hyperbilirubinaemia and elevated ferritin, raising the likelihood of both autoimmune haemolytic anaemia and HLH. He tested positive for Epstein-Barr virus (EBV), and bone marrow biopsy revealed hypercellular marrow with haemophagocytosis and no evidence of malignancy. High dose steroids were initiated with significant improvement in haemoglobin, resulting in a final diagnosis of HLH secondary to acute EBV infection. The patient was discharged on continued high-dose prednisone with planned taper and consideration of outpatient rituximab therapy for 4 weeks. High clinical suspicion and prompt evaluation were critical to early treatment and decreased morbidity.

Amelioration of Murine Macrophage Activation Syndrome by Monomethyl Fumarate in Both a Heme Oxygenase 1-Dependent and Heme Oxygenase 1-Independent Manner

OBJECTIVE

Macrophage activation syndrome (MAS) is characterized by increased serum levels of ferritin and heme oxygenase 1 (HO-1), and yet no known function is ascribed to these molecules in MAS. Because HO-1 is antiinflammatory, we hypothesized that pharmacologic activation of HO-1 could ameliorate MAS disease activity. Dimethyl fumarate (DMF), a treatment approved by the US Food and Drug Administration for multiple sclerosis, activates HO-1. Monomethyl fumarate (MMF) is the active metabolite of DMF. We therefore evaluated whether MMF could elicit HO-1-dependent therapeutic improvements in a murine model of MAS.

METHODS

We induced MAS by repeated activation of Toll-like receptor 9 (TLR-9) in wild-type and myeloid-specific HO-1-deficient mice. MMF was administered twice daily to test its efficacy. We assessed organ weights, serum cytokine levels, histologic features of the spleen and liver tissue, and complete blood cell counts to evaluate disease activity. Statistical testing was performed using Student's t-test or by 2-way analysis of variance as appropriate.

RESULTS

The presence of HO-1 was required for the majority of TLR-9-induced interleukin-10 (IL-10). IL-10 production in TLR-9-induced MAS was found to correlate with the myeloid-HO-1 gene dose in myeloid cells (P < 0.001). MMF treatment increased the levels of HO-1 in splenic macrophages by ~2-fold (P < 0.01), increased serum levels of IL-10 in an HO-1-dependent manner in mice with TLR-9-induced MAS (P < 0.005), and improved multiple disease parameters in both an HO-1-dependent and HO-1-independent manner.

CONCLUSION

TLR-9-induced production of IL-10 is regulated by HO-1 activity both in vitro and in vivo. Therapeutic enhancement of the HO-1/IL-10 axis in a murine model was able to significantly ameliorate MAS disease activity. These results suggest that HO-1 may be viable as a MAS therapeutic target, and treatment with DMF and MMF should be considered in future investigations of MAS therapy.

Functional and genetic testing in adults with HLH reveals an inflammatory profile rather than a cytotoxicity defect

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory condition. Primary HLH occurs early in life as a result of monogenic biallelic mutations affecting lymphocyte cytotoxicity. Secondary HLH occurs mostly in adults secondary to infection, lymphoma, or rheumatic disease. In this latter setting, lymphocyte cytotoxicity status is not known. We conducted a systematic evaluation of natural killer (NK) cell cytotoxicity in adult patients with secondary HLH. Adult patients with secondary HLH were prospectively studied ex vivo for total lymphocyte count and subtype, NK cell phenotype, perforin expression and degranulation, and natural or antibody-dependent cell cytotoxicity, in comparison with patients affected by the same underlying disease without HLH (disease controls [DCs]) and with healthy controls (HCs). Screening for variants of cytotoxity genes was systematically performed. 68 patients were included in the HLH group and 34 each in the DC and HC groups. In HLH patients, severe and transient lymphopenia, activated NK cell phenotype (eg, increased CD69, ICAM-1, HLADR, and CCR5 expression), and decreased capacity of interferon γ production were observed; mean perforin expression was normal; and degranulation tests and NK cell cytotoxicity were not different from those in DCs. A monoallelic variant of uncertain significance affecting a lymphocyte cytotoxicity gene or the perforin variant A91V was observed in almost 50% of the patients. We detected no major intrinsic cytotoxicity dysfunction in secondary HLH patients compared with DCs and no predicted pathogenic gene variant. The activated NK phenotype profile associated with decreased interferon γ production seems similar to those of other hyperinflammatory diseases such as sepsis or systemic juvenile idiopathic arthritis.

A network-informed analysis of SARS-CoV-2 and hemophagocytic lymphohistiocytosis genes' interactions points to Neutrophil extracellular traps as mediators of thrombosis in COVID-19

Abnormal coagulation and an increased risk of thrombosis are features of severe COVID-19, with parallels proposed with hemophagocytic lymphohistiocytosis (HLH), a life-threating condition associated with hyperinflammation. The presence of HLH was described in severely ill patients during the H1N1 influenza epidemic, presenting with pulmonary vascular thrombosis. We tested the hypothesis that genes causing primary HLH regulate pathways linking pulmonary thromboembolism to the presence of SARS-CoV-2 using novel network-informed computational algorithms. This approach led to the identification of Neutrophils Extracellular Traps (NETs) as plausible mediators of vascular thrombosis in severe COVID-19 in children and adults. Taken together, the network-informed analysis led us to propose the following model: the release of NETs in response to inflammatory signals acting in concert with SARS-CoV-2 damage the endothelium and direct platelet-activation promoting abnormal coagulation leading to serious complications of COVID-19. The underlying hypothesis is that genetic and/or environmental conditions that favor the release of NETs may predispose individuals to thrombotic complications of COVID-19 due to an increase risk of abnormal coagulation. This would be a common pathogenic mechanism in conditions including autoimmune/infectious diseases, hematologic and metabolic disorders.

Pathology of macrophage activation syndrome in humanized NSGS mice

"Humanized" immunodeficient mice generated via the transplantation of CD34+ human hematopoietic stem cells (hHSC) are an important preclinical model system. The triple transgenic NOD.Cg-Prkdc^scidIl2rg^tm1Wjl Tg(CMV-IL3,CSF2,KITLG)1Eav/MloySzJ (NSGS) mouse line is increasingly used as recipient for CD34+ hHSC engraftment. NSGS mice combine the features of the highly immunodeficient NSG mice with transgenic expression of the human myeloid stimulatory cytokines GM-CSF, IL-3, and Kit ligand. While generating humanized NSGS (huNSGS) mice from two independent cohorts, we encountered a fatal macrophage activation syndrome (MAS)-like phenotype resulting from the transplantation of CD34+ hHSC. huNSGS mice exhibiting this phenotype declined clinically starting at approximately 10 weeks following CD34+ hHSC engraftment, with all mice requiring euthanasia by 16 weeks. Gross changes comprised small, irregular liver, splenomegaly, cardiomegaly, and generalized pallor. Hematological abnormalities included severe thrombocytopenia and anemia. Pathologically, huNSGS spontaneously developed a disseminated histiocytosis with infiltrates of activated macrophages and hemophagocytosis predominantly affecting the liver, spleen, bone marrow, and pancreas. The infiltrates were chimeric with a mixture of human and mouse macrophages. Immunohistochemistry suggested activation of the inflammasome in both human and murine macrophages. Active Epstein-Barr virus infection was not a feature. Although the affected mice exhibited robust chimerism of the spleen and bone marrow, the phenotype often developed in the face of low chimerism of the peripheral blood. Given the high penetrance and early lethality associated with the MAS-like phenotype here described, we urge caution when considering the use of huNSGS mice for the development of long-term studies.

Hereditary haemochromatosis, haemophagocytic lymphohistiocytosis and COVID-19

BACKGROUND

Syndromes of iron overload have been shown to increase the risk of severe clinical disease in viral infections. Immune dysfunction is similarly described in hereditary haemochromatosis (HH). We present here the case of a 51-year-old man who developed severe coronavirus disease 2019 (COVID-19) complicated by suspected haemophagocytic lymphohistiocytosis (HLH). He was found to have HH post-mortem and we propose a link between his iron overload and the development of severe COVID-19.

CASE REPORT

The initial clinical presentation consisted of cough, shortness of breath and fever. Pancytopenia, markedly elevated ferritin and d-dimer were present. Computed tomography (CT) showed bilateral ground glass changes consistent with COVID-19, widespread lymphadenopathy and splenomegaly. A subsequent combined nose and throat swab was positive for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). HLH was suspected based upon the H-score and Anakinra, an IL-1 receptor antagonist, was commenced. Liver function acutely worsened and magnetic resonance cholangiopancreatography (MRCP) revealed hepatic haemosiderosis. Intense splenic and cervical lymph node uptake were seen on a positron emission tomography (PET) scan and high doses of intravenous steroids were administered due to concerns over haematological malignancy.

RESULTS

Day fourteen of admission heralded the start of progressive clinical deterioration with rapid increase in oxygen demands. Continuous positive airway pressure (CPAP) was trialled without success and the patient unfortunately died seventeen days into admission. Results returned after his death showed homozygous C282Y mutation of the HFE gene consistent with a diagnosis of HH. Post-mortem examination revealed widespread haemosiderin deposition in the liver along with lung pathology in keeping with severe COVID-19 and widespread splenic infarctions.

CONCLUSION

An association between HH and COVID-19 is not currently described in the literature. What does exist, however, is an evidence base for the detrimental impacts iron overload has on viral infections in general and the negative effects of HH on the immune system. We therefore postulate that the underlying metabolic and immune disturbances seen in HH should be considered a potential risk factor for the development of severe COVID-19. This case also adds to the evidence that hyperinflammation appears to be a unique and interesting characteristic of this novel viral disease.

Primary Cutaneous Gamma/Delta T-cell Lymphoma and Hemophagocytic Lymphohistiocytosis Associated With AIDS

Primary cutaneous gamma delta T-cell lymphoma (PCGD-TCL) is a rare lymphoma that makes up less than 1% of all cutaneous T-cell lymphomas. Patients with PCGD-TCL typically present with rapidly progressing plaques and ulceronecrotic nodules most frequently located on extremities without lymph node or bone marrow involvement. The overall prognosis is poor with a median overall survival of approximately 15 months. This case highlights a patient with concomitant PCGD-TCL, hemophagocytic lymphohistiocytosis, and human immunodeficiency virus-1-acquired immunodeficiency syndrome. There is a paucity of case reports describing PCGD-TCL and there are no evidence-based treatment recommendations. Further studies are needed to optimize strategies to treat patients with these diseases.

Molecular and Cellular Mechanisms of Arthritis in Children and Adults: New Perspectives on Applied Photobiomodulation

Juvenile idiopathic arthritis and adult rheumatoid arthritis are two major groups with chronic joint pain and inflammation, extra-articular manifestations, and high risk of comorbidities, which can cause physical and ocular disability, as well as create great socio-economic pressure worldwide. The pathogenesis of arthritis manifested in childhood and adulthood is multifactorial, unclear, and overly complex, in which immunity plays an important role. Although there are more and more biological agents with different mechanisms of action for the treatment of arthritis, the results are not as expected, because there are partial responses or non-responsive patients to these compounds, high therapeutic costs, side effects, and so on; therefore, we must turn our attention to other therapeutic modalities. Updating knowledge on molecular and cellular mechanisms in the comparative pathogenesis of chronic arthritis in both children and adults is necessary in the early and correct approach to treatment. Photobiomodulation (PBM) represents a good option, offering cost-effective advantages over drug therapy, with a quicker, more positive response to treatment and no side effects. The successful management of PBM in arthritis is based on the clinician's ability to evaluate correctly the inflammatory status of the patient, to seek the optimal solution, to choose the best technology with the best physical parameters, and to select the mode of action to target very precisely the immune system and the molecular signaling pathways at the molecular level with the exact amount of quantum light energy in order to obtain the desired immune modulation and the remission of the disease. Light is a very powerful tool in medicine because it can simultaneously target many cascades of immune system activation in comparison with drugs, so PBM can perform very delicate tasks inside our cells to modulate cellular dysfunctions, helping to initiate self-organization phenomena and finally, healing the disease. Interdisciplinary teams should work diligently to meet these needs by also using single-cell imaging devices for multispectral laser photobiomodulation on immune cells.

Hemophagocytic lymphohistiocytosis: a review inspired by the COVID-19 pandemic

Hemophagocytic syndrome (HPS) or hemophagocytic lymphohistiocytosis (HLH) is an acute and rapidly progressive systemic inflammatory disorder characterized by cytopenia, excessive cytokine production, and hyperferritinemia. Common clinical manifestations of HLH are acute unremitting fever, lymphadenopathy, hepatosplenomegaly, and multiorgan failure. Due to a massive cytokine release, this clinical condition is considered as a cytokine storm syndrome. HPS has primary and acquired (secondary, reactive) forms. Its primary form is mostly seen in childhood and caused by various mutations with genetic inheritance and, therefore, is called familial HLH. Secondary HLH may be caused in the presence of an underlying disorder, that is, secondary to a malignant, infectious, or autoimmune/autoinflammatory stimulus. This paper aims to review the pathogenesis and the clinical picture of HLH, and its severe complication, the cytokine storm, with a special emphasis on the developed classification criteria sets for rheumatologists, since COVID-19 infection has clinical symptoms resembling those of the common rheumatologic conditions and possibly triggers HLH. MED-LINE/Pubmed was searched from inception to April 2020, and the following terms were used for data searching: “hemophagocytic syndrome” OR “macrophage activation syndrome” OR “hemophagocytic lymphohistiocytosis”, OR “cytokine storm”. Finally, AND “COVID-19” was included in this algorithm. The selection is restricted to the past 5 years and limited numbers of earlier key references were manually selected. Only full-text manuscripts, published in an English language peer-reviewed journal were included. Manuscript selection procedure and numbers are given in Fig. 2. Briefly, the database search with the following terms of “Hemophagocytic syndrome” OR “Macrophage activation syndrome” OR “Hemophagocytic lymphohistiocytosis” OR “Cytokine storm” yielded 6744 results from inception to April 2020. The selection is restricted to the past 5 years and only limited numbers of earlier key references were selected, and this algorithm resulted in 3080 manuscripts. The addition of (AND “COVID-19”) resulted in 115 publications of which 47 studies, together with four sections of an online book were used in the final review. No statistical method was used. HLH is triggered by genetic conditions, infections, malignancies, autoimmune-autoinflammatory diseases, and some drugs. In COVID-19 patients, secondary HLH and cytokine storm may be responsible for unexplained progressive fever, cytopenia, ARDS, neurological and renal impairment. Differentiation between the primary and secondary forms of HLH is utterly important, since primary form of HLH requires complicated treatments such as hematopoietic stem cell transplantation. Further studies addressing the performance of HScore and other recommendations in the classification of these patients is necessary.

The NAIP/NLRC4 inflammasome in infection and pathology

In this review we give an overview of the NAIP/NLRC4 activation mechanism as well as the described roles of this inflammasome, with a focus on in vivo infection and pathology. After ligand recognition by NAIP sensor proteins the NAIP/NLRC4 inflammasome forms through oligomerization with the NLRC4 adaptor to activate Caspase-1. The activating ligands are intracellular bacterial flagellin or type-3 secretion system components, delivered by pathogens. In vivo experiments indicate a role in macrophages during lung, spleen and liver infection and systemic sepsis like conditions, as well as in intestinal epithelial cells. Upon NAIP/NLRC4 activation in the intestine, epithelial cell extrusion is triggered in addition to the canonical inflammasome outcomes of cytokine cleavage and pyroptosis. Human patients with auto-activating mutations in NLRC4 present with an autoinflammatory syndrome including enterocolitis. Although one of the better understood inflammasomes in terms of mechanism, tissue specific functions of NAIP/NLRC4 are only beginning to be understood.

Synergistic Signaling of TLR and IFNα/β Facilitates Escape of IL-18 Expression from Endotoxin Tolerance

Rationale: IL-18 is a member of the IL-1 cytokine family, and elevated blood IL-18 concentrations associate with disease activity in macrophage activation syndrome (MAS) and poor clinical outcomes in severe inflammatory and septic conditions.

Objectives: Although recent investigations provide mechanistic evidence for a contribution of IL-18 to inflammation and hyperinflammation in sepsis and MAS, we sought to study regulatory mechanisms underlying human IL-18 expression.

Methods: Samples from in vivo and in vitro endotoxin rechallenge experiments, patients with inflammatory disease, and isolated human monocytes treated with various stimulants and drugs were tested for cytokine gene and protein expression. Serum IL-18 expression with or without JAK/STAT inhibition was analyzed in two MAS mouse models and in a patient with recurrent MAS.

Measurements and Main Results: Peripheral blood and monocytic IL-18 expression escaped LPS-induced immunoparalysis. LPS-stimulated primary human monocytes revealed specific IL-18 expression kinetics controlled by IFNα/β signaling. JAK/STAT inhibition or IFNβ neutralization during LPS stimulation blunted cytokine expression. Similarly, microtubule-destabilizing drugs abrogated LPS-induced IL18 expression, but this effect could be fully reversed by addition of IFNα/β. Ex vivo analysis of inflammatory disease patients’ whole blood revealed strong correlation of type I IFN score and IL18 expression, whereas JAK/STAT inhibition strongly reduced IL-18 serum levels in two MAS mouse models and in a patient with recurrent MAS.

Conclusions: Our data indicate that IL-18 (but not IL-1β) production from human monocytes requires cooperative Toll-like receptor and IFNα/β signaling. Interference with IFNα/β expression or signaling following JAK/STAT inhibition may control catastrophic hyperinflammation in MAS.

Macrophage activation syndrome associated with adult-onset Still's disease: a multicenter retrospective analysis

OBJECTIVES

To explore the clinical features, treatments, and prognostic factors of adult-onset Still's disease (AOSD)-associated macrophage activation syndrome (MAS), we conducted a multicenter retrospective clinical study of AOSD-associated MAS patients.

METHODS

AOSD patients were collected from six tertiary hospitals in China. Medical charts were reviewed and clinical information was recorded and analyzed.

RESULTS

There were 447 AOSD patients enrolled into this retrospective clinical study. Among them, 55 were diagnosed with MAS. Liver dysfunction was the most reliable predictive factor for the screening of MAS in AOSD patients (OR = 75.744, 95%CI = 23.015-249.284, p < 0.0001). In multivariate analysis, clinical features including platelets < 100 × 10⁹/L (OR = 9.546, p = 0.005), aspartate transaminase (AST) > 120 U/L (OR = 25.853, p < 0.0001), triglycerides > 3 mmol/L (OR = 12.9833, p = 0.011)), ferritin > 1500 ng/mL (OR = 5.513, p = 0.050), as well as hemophagocytosis in bone puncture (OR = 18.132, p = 0.001) were highly associated with the occurrence of MAS. The mortality rate of total AOSD patients was 4.47%, MAS was the main cause of death in AOSD patients (OR = 11.705, 95%CI = 4.783-28.647, p < 0.0001). PLT ≤ 100 × 10⁹/L (p = 0.0001), fibrinogen < 1.5 g/L (p = 0.0286), splenomegaly (p = 0.0002), and liver dysfunction (p = 0.0008) highly suggested poor prognosis.

CONCLUSION

MAS occurrence is the major cause of death in AOSD patients. Notable liver dysfunction, as well as splenomegaly, low number of platelets or neutrophils, high levels of serum ferritin, and reduced level of fibrinogen are risk factors for poor outcome. Key Points • This is a multicenter retrospective study of AOSD-associated MAS with large number of cases.

Usefulness of soluble CD163 as a biomarker for macrophage activation syndrome associated with systemic lupus erythematosus

OBJECTIVE

We aimed to study the usefulness of serum soluble CD163 (sCD163) as a biomarker for macrophage activation syndrome (MAS) associated with systemic lupus erythematosus (SLE).

METHODS

Serum sCD163 levels were retrospectively measured by enzyme-linked immunosorbent assay for SLE patients associated with MAS (SLE-MAS), lupus nephritis (LN), or autoimmune hemolytic anemia (AIHA) and/or immune thrombocytopenia (ITP) and healthy controls (HCs). Posttreatment samples were also evaluated in the available SLE-MAS patients. The associations between serum sCD163 levels and clinical information were statistically analyzed.

RESULTS

The serum sCD163 levels in SLE-MAS, LN and SLE-AIHA/ITP groups were significantly higher than those in HCs (n = 17, 29, 13, and 68, respectively; p < 0.01 for all comparisons). In addition, the serum sCD163 levels in the SLE-MAS group were even higher than those in the LN and SLE-AIHA/ITP groups (p < 0.01 for both comparisons). Serum sCD163 levels were correlated with the SLE Disease Activity Index 2000 scores (r = 0.53), whereas they were not correlated with the serum ferritin levels. With the determined cut-off value, the sensitivity and specificity of serum sCD163 for the diagnosis of SLE-MAS were 59% and 86%, respectively. Retesting showed that the serum sCD163 levels decreased significantly following treatment in parallel with disease amelioration in the SLE-MAS group (p < 0.01).

CONCLUSIONS

The present study suggests the usefulness of serum sCD163 as a diagnostic and disease-activity biomarker for SLE-associated MAS. Serum sCD163 might also have a different role as a biomarker for SLE-associated MAS than serum ferritin does.

The extended understanding of chronic granulomatous disease

PURPOSE OF REVIEW

We briefly address the advances in genetics, pathophysiology, and phenotypes of chronic granulomatous disease (CGD). This is one of the most studied primary immunodeficiencies, which comprise mutations in genes encoding the different subunits of the NADPH oxidase system. Those mutations lead to defective reactive oxygen species production, and consequently a failure to eliminate pathogens.

RECENT FINDINGS

Patients with CGD are susceptible to fungal, bacterial, and parasitic infections. Other symptoms, as systemic adverse effects to BCG vaccine and hyperinflammation, are also important clinical conditions in this disease. This wide-ranging clinical spectrum of CGD comes from heterogeneity of mutations, X-linked-CGD or autosomal recessive inheritance, and diverse environmental pressure factors. Early accurate diagnosis and prompt treatment are necessary to diminish the consequences of the disease. The most used diagnostic tests are dihydrorhodamine, cytochrome c reduction, and luminol-enhanced chemiluminescence assay.

SUMMARY

The determination of mutations is essential for diagnosis confirmation and genetic counseling. CGD treatment usually includes prophylactic antibiotics and antifungals. Prophylactic recombinant human interferon-γ, immunosuppressors or immune modulators may be, respectively, indicated for preventing infections or inflammatory manifestations. Hematopoietic stem cell transplantation and gene therapy are currently the available options for curative treatment of CGD.

A human immune dysregulation syndrome characterized by severe hyperinflammation with a homozygous nonsense Roquin-1 mutation

Hyperinflammatory syndromes are life-threatening disorders caused by overzealous immune cell activation and cytokine release, often resulting from defects in negative feedback mechanisms. In the quintessential hyperinflammatory syndrome familial hemophagocytic lymphohistiocytosis (HLH), inborn errors of cytotoxicity result in effector cell accumulation, immune dysregulation and, if untreated, tissue damage and death. Here, we describe a human case with a homozygous nonsense R688* RC3H1 mutation suffering from hyperinflammation, presenting as relapsing HLH. RC3H1 encodes Roquin-1, a posttranscriptional repressor of immune-regulatory proteins such as ICOS, OX40 and TNF. Comparing the R688* variant with the murine M199R variant reveals a phenotypic resemblance, both in immune cell activation, hypercytokinemia and disease development. Mechanistically, R688* Roquin-1 fails to localize to P-bodies and interact with the CCR4-NOT deadenylation complex, impeding mRNA decay and dysregulating cytokine production. The results from this unique case suggest that impaired Roquin-1 function provokes hyperinflammation by a failure to quench immune activation.

Roquin-1 is a posttranscriptional regulator that controls the expression of many immune-related genes such as ICOS and TNFA. Here, the authors report a homozygous R688* loss of function mutation in Roquin-1 in a patient with syndromic uncontrolled hyperinflammation associated with immune cell activation and hypercytokinemia.

Linfohistiocitosis hemofagocítica en trasplante renal

La linfohistiocitosis hemofagocítica (LHH) posterior al trasplante renal hace referencia a un estado hiperinflamatorio grave, asociado a la activación no controlada de los linfocitos T citotóxicos y macrófagos por causa infecciosas y/o secundaria al tratamiento inmunosupresor. Las causas más prevalentes dentro de las infecciones son la histoplasmosis, la tuberculosis y las infecciones por virus herpes. Se caracteriza por fiebre, organomegalias, citopenias, hiperferritinemia, hipertrigliceridemia y/o hipofibrinogenemia; puede acompañarse con hemofagocitosis documentada en la médula ósea, el hígado u otros órganos. Su curso puede ser fulminante con progresión a falla multisistémica y la muerte.El tratamiento va enfocado a controlar tempranamente la causa desencadenante, reducir la inmunosupresión y controlar la inflamación. En pocos casos es necesario el uso de otros inmunosupresores, quimioterapia o, en situaciones muy seleccionadas, se puede requerir el trasplante de médula ósea.

Clinical features of macrophage activation syndrome as the onset manifestation of juvenile systemic lupus erythematosus

Objectives

Macrophage activation syndrome (MAS) is a severe complication of juvenile systemic lupus erythematosus (jSLE). However, little is known about the association between these conditions, especially in terms of MAS as the initial manifestation of jSLE. The aim of this study was to determine the clinical features of MAS as the initial manifestation of jSLE.

Methods

We carried out a retrospective review of the clinical features of MAS cases diagnosed concomitantly with jSLE from 2004 to 2016. Data from these patients were compared with those from a control group consisting of jSLE patients without MAS.

Results

Eleven (23.9%) of the 46 patients recruited for this study were diagnosed with MAS during the initial stage of jSLE. The between-group comparisons demonstrated that fever, leucopenia, hyperferritinaemia and increased aspartate aminotransferase were more frequently observed in jSLE patients with MAS than in controls (P<0.01). Importantly, neurological symptoms were significantly more common in patients with MAS than in controls (P<0.01), with 6 (54.6%) of the 11 MAS patients affected. For treatment, all 11 patients with both jSLE and MAS were administered CSs upon diagnosis, and 7 received immunosuppressants. No patient involved in this study died.

Conclusion

MAS can develop as the initial manifestation of jSLE. MAS with jSLE should be suspected in patients with fever, hyperferritinaemia, cytopenia and liver disorder. In addition, we found that jSLE patients with MAS had more neurological symptoms than those without. All patients with MAS were successfully treated with CSs. Early diagnosis and intensive therapy are essential in improving clinical outcomes.

Prevalence and Outcome of Secondary Hemophagocytic Lymphohistiocytosis Among SIRS Patients: Results from a Prospective Cohort Study

Secondary hemophagocytic lymphohistiocytosis (sHLH) is a life-threatening condition clinically presenting as SIRS (Systemic Inflammatory Response Syndrome). However, there is no comprehensive data concerning diagnostic algorithms, prevalence, outcome and biomarker performance in SIRS patients. We conducted a prospective observational cohort study on 451 consecutive patients fulfilling ≥2 SIRS criteria. The Hscore and the HLH-2004 criteria were used to determine the presence of sHLH, and the correlation of the screening-biomarkers ferritin, sCD25, and sCD163 with both scores was assessed. Out of 451 standard-care SIRS patients, five patients had high Hscores (≥169), suggesting incipient or HLH-like disease, and these patients were in urgent need for intensified therapy. However, none of these patients fulfilled five HLH-2004 criteria required for formal diagnosis. From the studied biomarkers, ferritin correlated strongest to both the HLH-2004 criteria and the Hscore (rs = 0.72, 0.41, respectively), and was the best predictor of 30-day survival (HR:1.012 per 100 μg/L, 95% CI: 1.004-1.021), when adjusted for patient's age, sex, bacteremia and malignant underlying-disease. Also, the HLH-2004 (HR per point increase: 1.435, 95% CI: 1.1012-2.086) and the Hscore (HR per point increase:1.011, 95% CI: 1.002-1.020) were independent predictors of 30-day-survival. The Hscore detected patients in hyperinflammatory states requiring urgent therapy escalation. Degrees of hyperinflammation, as assessed by ferritin and both HLH scores, are associated with worse outcomes.

Cross-regulation of defective endolysosome trafficking and enhanced autophagy through TFEB in UNC13D deficiency

Several lines of evidence support the occurrence of cross-regulation between the endocytic pathway and autophagy, but the molecular mechanisms regulating this process are not well-understood. Here, we show that the calcium sensor UNC13D regulates the molecular mechanism of late endosomal trafficking and endosomal maturation, and defects in UNC13D lead to macroautophagy upregulation. unc13d-null cells showed impaired endosomal trafficking and defective endocytic flux. The defective phenotypes were rescued by the expression of UNC13D but not by its STX7-binding-deficient mutant. This defective endosomal function in UNC13D-deficient cells resulted in increased autophagic flux, increased long-lived protein degradation, decreased SQSTM1/p62 protein levels and increased autolysosome formation as determined by biochemical, microscopy and structural methods. The autophagic phenotype was not associated with increased recruitment of the UNC13D-binding proteins and autophagy regulators, RAB11 or VAMP8, but was caused, at least in part, by TFEB-mediated upregulation of a subset of autophagic and lysosomal genes, including Atg9b. Downregulation of TFEB decreased Atg9b levels and decreased macroautophagy in unc13d-null cells. UNC13D upregulation corrected the defects in endolysosomal trafficking and decreased the number of accumulated autophagosomes in a cellular model of the lysosomal-storage disorder cystinosis, under both fed and starvation conditions, identifying UNC13D as an important new regulatory molecule of autophagy regulation in cells with lysosomal disorders. Abbreviations ACTB: actin, beta; CTSB: cathepsin B; EEA1: early endosome antigen 1; ESCRT: endosomal sorting complex required for transport; FHL3: familial hemophagocytic; lymphohistiocytosis type 3; HEX: hexosaminidase; HLH: hemophagocytic lymphohistiocytosis; LSD: lysosomal storage disorder; MEF: mouse embryonic fibroblast; SEM: standard errors of the mean; SNARE: soluble n-ethylmaleimide-sensitive-factor attachment receptor; STX: syntaxin; SYT7: synaptotagmin VII; TFE3: transcription factor E3; TFEB: transcription factor EB; TIRF: total internal reflection fluorescence ULK1: unc-51 like kinase 1; UNC13D: unc-13 homolog d; VAMP: vesicle-associate membrane protein; WT: wild-type.

Immune myopathy with large histiocyte-related myofiber necrosis

OBJECTIVE

To describe the features of a new, pathologically distinctive, acquired myopathy with an unusual pattern of scattered necrotic muscle fibers that are neighbored, surrounded, or invaded, by large, often multinucleated, histiocytic cells.

METHODS

Retrospective review of records and muscle pathology of 4 patients.

RESULTS

Clinical features common to our patients included muscle pain and proximal, symmetric, moderate to severe, weakness in the arms and legs progressing over 1-4 weeks. Patients had other associated systemic disorders, including anemia in all, and hemophagocytic lymphohistiocytosis, hepatic disease, Raynaud phenomenon, metastatic cancer, and cardiomyopathy, in 1 patient each. Serum creatine kinase (CK) levels at presentation were very high, ranging from 10,000 to 102,000 U/L. Three patients improved within 3 months after treatment. Muscle pathology included scattered necrotic muscle fibers with cytoplasm that stained for C_5b-9 complement, especially around fiber peripheries, pale on nicotinamide adenine dinucleotide and often dark on hematoxylin & eosin. Large, often multinucleated, cells with features of histiocytes, including anatomical features on electron microscopy and immunostaining for major histocompatibility complex Class I and histiocyte markers (HAM56, CD68, CD163, and S100), were usually closely apposed to the surface of, or invaded, necrotic myofibers.

CONCLUSIONS

Patients with large-histiocyte-associated myopathy (LHIM) had a subacute onset of proximal predominant weakness, associated systemic disorders, very high serum CK, and a pathologically distinctive pattern of large histiocyte-associated muscle fiber necrosis. LHIM may be caused by an autoimmune, histiocyte-mediated attack directed against muscle fibers.

Posttransplant Hemophagocytic Lymphohistiocytosis Driven by Myeloid Cytokines and Vicious Cycles of T-Cell and Macrophage Activation in Humanized Mice

Hemophagocytic lymphohistiocytosis (HLH) has recently been increasingly reported as an important complication after stem cell transplantation, in line with the increase in the number of HLA-mismatched transplantation. Although previous clinical studies have shown an elevation of inflammatory cytokines in patients with HLH after hematopoietic stem cell transplantation, as well as those after viral infection or autoimmune disease, the disease pathogenesis remains poorly understood. Here we explored this issue in humanized mice with functional human lymphohematopoietic systems, which were constructed by transplantation of human CD34⁺ cells alone, or along with human fetal thymus into NOD/SCID/γc^−/− (NSG) or NSG mice carrying human SCF/GM-CSF/IL-3 transgenes (SGM3). In comparison with humanized NSG (huNSG) mice, huSGM3 mice had higher human myeloid reconstitution and aggressive expansion of human CD4⁺ memory T cells, particularly in the absence of human thymus. Although all huNSG mice appeared healthy throughout the observation period of over 20 weeks, huSGM3 mice developed fatal disease characterized by severe human T cell and macrophage infiltrations to systemic organs. HuSGM3 mice also showed severe anemia and thrombocytopenia with hypoplastic bone marrow, but increased reticulocyte counts in blood. In addition, huSGM3 mice showed a significant elevation in human inflammatory cytokines including IL-6, IL-18, IFN-α, and TNF-γ, faithfully reproducing HLH in clinical situations. Our study suggests that posttransplant HLH is triggered by alloresponses (or xenoresponses in our model), driven by myeloid cytokines, and exacerbated by vicious cycles of T-cell and macrophage activation.

The Immunology of Macrophage Activation Syndrome

Synonymous with secondary hemophagocytic lymphohistiocytosis, macrophage activation syndrome (MAS) is a term used by rheumatologists to describe a potentially life-threatening complication of systemic inflammatory disorders, most commonly systemic juvenile idiopathic arthritis (sJIA) and systemic lupus erythematosus (SLE). Clinical and laboratory features of MAS include sustained fever, hyperferritinemia, pancytopenia, fibrinolytic coagulopathy, and liver dysfunction. Soluble interleukin-2 receptor alpha chain (sCD25) and sCD163 may be elevated, and histopathology often reveals characteristic increased hemophagocytic activity in the bone marrow (and other tissues), with positive CD163 (histiocyte) staining. A common hypothesis as to the pathophysiology of many cases of MAS proposes a defect in lymphocyte cytolytic activity. Specific heterozygous gene mutations in familial HLH-associated cytolytic pathway genes (e.g., PRF1, UNC13D) have been linked to a substantial subset of MAS patients. In addition, the pro-inflammatory cytokine environment, particularly IL-6, has been shown to decrease NK cell cytolytic function. The inability of NK cells and cytolytic CD8 T cells to lyse infected and otherwise activated antigen presenting cells results in prolonged cell-to-cell (innate and adaptive immune cells) interactions and amplification of a pro-inflammatory cytokine cascade. The cytokine storm results in activation of macrophages, causing hemophagocytosis, as well as contributing to multi-organ dysfunction. In addition to macrophages, dendritic cells likely play a critical role in antigen presentation to cytolytic lymphocytes, as well as contributing to cytokine expression. Several cytokines, including tumor necrosis factor, interferon-gamma, and numerous interleukins (i.e., IL-1, IL-6, IL-18, IL-33), have been implicated in the cytokine cascade. In addition to broadly immunosuppressive therapies, novel cytokine targeted treatments are being explored to dampen the overly active immune response that is responsible for much of the pathology seen in MAS.

Specific sequences of infectious challenge lead to secondary hemophagocytic lymphohistiocytosis-like disease in mice

Secondary hemophagocytic lymphohistiocytosis (sHLH) is a highly mortal complication associated with sepsis. In adults, it is often seen in the setting of infections, especially viral infections, but the mechanisms that underlie pathogenesis are unknown. sHLH is characterized by a hyperinflammatory state and the presence hemophagocytosis. We found that sequential challenging of mice with a nonlethal dose of viral toll-like receptor (TLR) agonist followed by a nonlethal dose of TLR4 agonist, but not other permutations, produced a highly lethal state that recapitulates many aspects of human HLH. We found that this hyperinflammatory response could be recapitulated in vitro in bone marrow-derived macrophages. RNA sequencing analyses revealed dramatic up-regulation of the red-pulp macrophage lineage-defining transcription factor SpiC and its associated transcriptional program, which was also present in bone marrow macrophages sorted from patients with sHLH. Transcriptional profiling also revealed a unique metabolic transcriptional profile in these macrophages, and immunometabolic phenotyping revealed impaired mitochondrial function and oxidative metabolism and a reliance on glycolytic metabolism. Subsequently, we show that therapeutic administration of the glycolysis inhibitor 2-deoxyglucose was sufficient to rescue animals from HLH. Together, these data identify a potential mechanism for the pathogenesis of sHLH and a potentially useful therapeutic strategy for its treatment.

Kawasaki disease shock syndrome complicated with macrophage activation syndrome in a 5-month old boy: A case report

RATIONALE

Kawasaki disease (KD) is an acute febrile systemic vasculitis of unknown etiology and often occurs in children under 5 years old. During the acute phase, approximately 5% of children with KD develop hypotension and shock, a severe condition termed KD shock syndrome (KDSS). Macrophage activation syndrome (MAS), another life-threatening complication, has been reported to be associated with KD, although rarely. KDSS complicated with MAS is extremely rare. In this article, we present our experience in the diagnosis and treatment of KDSS complicated with MAS.

PATIENT CONCERNS

A 5-month boy with fever for 5 days was diagnosed with KD. After 2 doses of intravenous immunoglobulin and regular antiinflammatory treatment at a local hospital, the fever did not subdue. He was admitted to our department on the 10th day of illness. The boy developed KDSS on the 11th day of illness. In the mean time, the boy had hepatosplenomegaly, and laboratory tests showed hypertriglyceridemia, hypofibrinogenemia, decreased blood red cells and platelets, increased ferritin and soluble sIL2Rα, and reduced natural killer cell activity.

DIAGNOSIS

The patient had KDSS complicated with MAS.

INTERVENTIONS

Emergency antishock therapy along with high-dose steroid with a longer tapering course was carried out. Following these treatments, fever subsided and other symptoms and signs relieved, but progressive coronary dilatation occurred, warfarin was thereby administered.

OUTCOMES

The patient was discharged 30 days after hospitalization. Echocardiography at the 2 month follow-up showed regression of coronary aneurysm.

LESSONS

Laboratory testing is critical for the diagnosis of MAS and we recommend that 2009 HLH diagnostic criteria be used for the diagnosis of MAS in KD. Emergency treatment of shock and a longer course of high-dose steroid anti-inflammatory therapy are vital for the management of KDSS complicated with MAS.