Edward M. Behrens

Macrophage activation syndrome as part of systemic juvenile idiopathic arthritis: diagnosis, genetics, pathophysiology and treatment

Macrophage activation syndrome (MAS) is a severe, frequently fatal complication of systemic juvenile idiopathic arthritis (sJIA) with features of hemophagocytosis leading to coagulopathy, pancytopenia, and liver and central nervous system dysfunction. MAS is overt in 10% of children with sJIA but occurs subclinically in another 30–40%. It is difficult to distinguish sJIA disease flare from MAS. Development of criteria for establishing MAS as part of sJIA are under way and will hopefully prove sensitive and specific. Mutations in cytolytic pathway genes are increasingly being recognized in children who develop MAS as part of sJIA. Identification of these mutations may someday assist in MAS diagnosis. Defects in cytolytic genes have provided murine models of MAS to study pathophysiology and treatment. Recently, the first mouse model of MAS not requiring infection but rather dependent on repeated stimulation through Toll-like receptors was reported. This provides a model of MAS that may more accurately reflect MAS pathology in the setting of autoinflammation or autoimmunity. This model confirms the importance of a balance between pro- and anti-inflammatory cytokines. There has been remarkable progress in the use of anti-pro-inflammatory cytokine therapy, particularly against interleukin-1, in the treatment of secondary forms of MAS, such as in sJIA.

Successful treatment of severe paediatric rheumatic disease-associated macrophage activation syndrome with interleukin-1 inhibition following conventional immunosuppressive therapy: case series with 12 patients

SIR, Macrophage activation syndrome (MAS) belongs to the haemophagocytic lymphohistiocytic (HLH) disorders, and is one of the most feared complications of paediatric inflammatory diseases with mortality rates up to 53% [1]. Its early recognition and treatment are critical in improving outcome [2]. However, current therapeutics, including corticosteroids, ciclosporin and intravenous immunoglobulin (IVIG), do not work for all children, and the nextline treatments, such as etoposide, are associated with sepsis, a risk of secondary malignancy and up to 44% mortality rate [3]. A less immunosuppressive but effective targeted therapy is in demand. Anakinra, an IL-1 receptor antagonist, has been highly effective in treating systemic juvenile idiopathic arthritis (sJIA) [4], and MAS may occur in up to half of sJIA patients [5]. Recently, three case reports have demonstrated anakinra to effectively treat MAS as part of panniculitis, sJIA and adult onset Still’s disease [6–8]. Herein, we report the benefit of anakinra in 12 children with paediatric rheumatic disease-related MAS (prMAS). All patients at the Alberta Children’s Hospital and the Children’s Hospital of Philadelphia, who received anakinra between 2006 and 2009 for prMAS were studied retrospectively. The diagnosis of MAS was based on the combination of: (i) Ravelli’s preliminary criteria for sJIA-associated MAS [9] and (ii) HLH-2004 criteria for inherited HLH [10]. Resolution of MAS was defined by the HLH-2004 criteria [10], and included no fever, splenomegaly, cytopenia (haemoglobin 590 g/l, platelets 5100 10/l, absolute neutrophil count 5500 cells/ml) or hypertriglyceridaemia (>500 mg/l) and normalization of soluble CD25 (sCD25) if the test was performed. When prMAS occurred, all patients initially received corticosteroids (n1⁄4 12) and other immunosuppressants [IVIG (n1⁄4 9), ciclosporin (n1⁄4 10), etoposide (n1⁄4 2, one dose each) and etanercept (n1⁄4 1)] with limited benefit. Anakinra was given for better prMAS control. Etanercept and etoposide were discontinued when anakinra was initiated. In all other patients, anakinra was added to pre-existing MAS therapy at 2 mg/kg/day s.c. (maximum dose 100 mg/day) once daily. Laboratory measurements as per Ravelli’s and HLH-2004 criteria were measured before and after anakinra administration. CRP was additionally measured in selected patients. During hospitalization for prMAS, five patients were diagnosed with new-onset sJIA by the ILAR criteria, three patients with vasculitis using ACR criteria and one patient with acute rheumatic fever. Institutional Review Board approval was obtained from both institutions before the study for publication of the results of the case series. In total, 12 patients with prMAS were treated with anakinra between 2006 and 2009. Baseline characteristics are shown in Table 1. Before anakinra, five patients required intensive care, and potential infectious triggers were present in seven patients. All patients met diagnostic criteria for Ravelli’s sJIA-associated MAS [9]. Seven of 12 met the HLH-2004 criteria [10], including elevated ferritin (n1⁄4 12/12), haemophagocytosis in the bone marrow (n1⁄4 5/7), abnormal NK cell activity (n1⁄4 1/2) and elevated sCD25 (n1⁄4 4/6). The median hospitalization stay before anakinra was 11 (range 1–27) days. All patients achieved MAS remission after addition of anakinra within a median of 13 (range 2–19) days. Corticosteroids were discontinued by 6 weeks in seven patients. Of all laboratory parameters, CRP and ferritin correlated the best with MAS activity (Table 1). Median (interquartile range) CRP (n1⁄4 9/12) 2 days before the use of anakinra was 125 (95.5–183.5) mg/l compared with median 6.8 (1.9–8.9) mg/l 5 days after the use of anakinra (P1⁄4 0.0039). Patients were followed for a median of 22 (range 2–40) months, and all were in remission of MAS at the final follow-up with excellent control of the underlying rheumatic disease. There were no noted side effects from anakinra administration. We report resolution of severe prMAS following addition of anakinra to conventional immunosuppressive therapy. In these severely ill patients, anakinra was chosen over HLH-2004 treatment with etoposide and high-dose dexamethasone because of concern for sepsis, potential future malignancy and the high mortality rate associated with this protocol [3]. The clinical response was dramatic and rapid, occurring within days. All patients fully recovered, including five who had required intensive care support. In sJIA-related MAS, the mortality rate was reported in 2001 as 28% [2], yet all our patients with sJIA did well. Our three patients with vasculitis and one with rheumatic fever-associated MAS also remitted. Ravelli’s 2005 preliminary MAS criteria [9] allowed for early confirmation of MAS, although we also utilized ferritin, sCD25 and NK cell activity from the HLH-2004 criteria to confirm the diagnosis [10]. We attribute the excellent outcome in our patients to early diagnosis and immediate therapeutic intervention, including early use of anakinra. As all patients were treated with anakinra and traditional therapies, it is possible that the combination of medications contributed to the resolution of MAS. We therefore recommend anakinra in combination with high-dose corticosteroids, ciclosporin and IVIG, rather than as a sole agent. Further studies with larger patient numbers are required to better define

2016 Classification Criteria for Macrophage Activation Syndrome Complicating Systemic Juvenile Idiopathic Arthritis: A European League Against Rheumatism/American College of Rheumatology/Paediatric Rheumatology International Trials Organisation Collaborative Initiative

To develop criteria for the classification of macrophage activation syndrome (MAS) in patients with systemic juvenile idiopathic arthritis (JIA).

2016 Classification Criteria for Macrophage Activation Syndrome Complicating Systemic Juvenile Idiopathic Arthritis

To develop criteria for the classification of macrophage activation syndrome (MAS) in patients with systemic juvenile idiopathic arthritis (JIA). A multistep process, based on a combination of expert consensus and analysis of real patient data, was conducted. A panel of 28 experts was first asked to classify 428 patient profiles as having or not having MAS, based on clinical and laboratory features at the time of disease onset. The 428 profiles comprised 161 patients with systemic JIA—associated MAS and 267 patients with a condition that could potentially be confused with MAS (active systemic JIA without evidence of MAS, or systemic infection). Next, the ability of candidate criteria to classify individual patients as having MAS or not having MAS was assessed by evaluating the agreement between the classification yielded using the criteria and the consensus classification of the experts. The final criteria were selected in a consensus conference. Experts achieved consensus on the classification of 391 of the 428 patient profiles (91.4%). A total of 982 candidate criteria were tested statistically. The 37 best-performing criteria and 8 criteria obtained from the literature were evaluated at the consensus conference. During the conference, 82% consensus among experts was reached on the final MAS classification criteria. In validation analyses, these criteria had a sensitivity of 0.73 and a specificity of 0.99. Agreement between the classification (MAS or not MAS) obtained using the criteria and the original diagnosis made by the treating physician was high (κ=0.76). We have developed a set of classification criteria for MAS complicating systemic JIA and provided preliminary evidence of its validity. Use of these criteria will potentially improve understanding of MAS in systemic JIA and enhance efforts to discover effective therapies, by ensuring appropriate patient enrollment in studies.

Complement Receptor 3 Ligation of Dendritic Cells Suppresses Their Stimulatory Capacity

To activate T cells effectively, dendritic cells (DCs) must provide three separate signals, MHC-Ag, costimulatory molecules (such as CD80 and CD86), and proinflammatory cytokines (such as IL-12). These three signals are up-regulated in the presence of “danger signals” such as LPS or viral nucleic acids. Evidence suggests that DCs providing only the first two of these signals cannot successfully stimulate T cells. Apoptotic cells have been proposed to suppress DC immunogenicity through the ligation of apoptotic cell receptors. Complement receptor 3 (CR3) and CD36 have been suggested to be important in this process, although the mechanism by which this modulation occurs is still unclear. We demonstrate that ligation of CR3, but not CD36, directs DCs to increase surface MHC and costimulatory molecules, while suppressing inflammatory cytokine release. CR3 modulation of DCs does not require a type I IFN response, does not involve the specific regulation of the MyD88- or Toll/IL-1R domain-containing adaptor-inducing IFN-β-dependent TLR signaling pathways, and occurs even in the absence of danger signals. The functional outcome of this process is poor Ag-specific stimulation of CD4 and CD8 T cells by CR3-ligated DCs both in naive response as well as upon subsequent challenge with normal DCs. We propose that CR3 provides a “nondanger” signal that suppresses the stimulatory capacity of DCs.

Meta-analysis of shared genetic architecture across ten pediatric autoimmune diseases.

Genome-wide association studies (GWASs) have identified hundreds of susceptibility genes, including shared associations across clinically distinct autoimmune diseases. We performed an inverse χ2 meta-analysis across ten pediatric-age-of-onset autoimmune diseases (pAIDs) in a case-control study including more than 6,035 cases and 10,718 shared population-based controls. We identified 27 genome-wide significant loci associated with one or more pAIDs, mapping to in silico–replicated autoimmune-associated genes (including IL2RA) and new candidate loci with established immunoregulatory functions such as ADGRL2, TENM3, ANKRD30A, ADCY7 and CD40LG. The pAID-associated single-nucleotide polymorphisms (SNPs) were functionally enriched for deoxyribonuclease (DNase)-hypersensitivity sites, expression quantitative trait loci (eQTLs), microRNA (miRNA)-binding sites and coding variants. We also identified biologically correlated, pAID-associated candidate gene sets on the basis of immune cell expression profiling and found evidence of genetic sharing. Network and protein-interaction analyses demonstrated converging roles for the signaling pathways of type 1, 2 and 17 helper T cells (TH1, TH2 and TH17), JAK-STAT, interferon and interleukin in multiple autoimmune diseases.

Macrophage activation syndrome in rheumatic disease: what is the role of the antigen presenting cell?

Macrophage Activation Syndrome (MAS), alternatively referred to as secondary hemophagocytic lymphohistiocytosis (HLH), is a complication of many rheumatic diseases, most commonly Systemic Juvenile Idiopathic Arthritis (SJIA). MAS consists of a fulminant picture of pan-cytopenia, hectic high fevers, hepatosplenomegaly, lymphadenopathy, rash, and central nervous systemic inflammation. It can arise from genetic defects in the cytotoxic effector response of CD8+ T-cells, resulting in an inability to terminate antigen presentation, which in turn leads to uncontrolled immune activation. However, in the case of most rheumatic diseases, no such defect in cytotoxic killing is present. Little is known about what the contributions from the antigen presenting cells are in the pathogenesis of MAS. In fact, macrophages may be playing a regulatory, anti-inflammatory in MAS. We review the proposed pathogenesis of MAS/HLH, what role macrophages may play in the disease, and the relationship of MAS to its most common associated rheumatic disease, SJIA.

Life-threatening NLRC4-associated hyperinflammation successfully treated with IL-18 inhibition

NLRC4-inflammasome hyperactivity causes infantile-onset Macrophage Activation Syndrome and enterocolitis with extraordinary serum IL-18 elevation (NLRC4-MAS). Herein, we report a critically ill infant with severe, refractory NLRC4-MAS who showed sustained response to treatment with experimental IL-18 inhibition.

Genetic Defects in Cytolysis in Macrophage Activation Syndrome

Macrophage activation syndrome (MAS), typically presenting beyond the first year of life, is an often lethal cousin of familial hemophagocytic lymphohistiocytosis (fHLH). Defects in natural killer (NK) cell and CD8 T cell cytotoxicity result in a pro-inflammatory cytokine storm, cytopenia, coagulopathy, and multi-organ system dysfunction. MAS can occur in association with infections (herpes viruses), cancer (leukemia), immune deficient states (post-transplantation), and in autoimmune (systemic lupus erythematosus) and autoinflammatory conditions (systemic juvenile idiopathic arthritis). The distinction between fHLH, the result of homozygous defects in cytolytic pathway genes, and MAS is becoming blurred with the identification of single or multiple mutations in the same cytolytic pathway genes in patients with later onset MAS. Here, we review the literature and present novel cytolytic pathway gene mutations identified in children with MAS. We study the inhibitory effect of one these novel mutations on NK cell function to suggest a direct link between fHLH and MAS.

Interferon-γ mediates anemia but is dispensable for fulminant toll-like receptor 9-induced macrophage activation syndrome and hemophagocytosis in mice.

OBJECTIVE Macrophage activation syndrome (MAS) is a devastating cytokine storm syndrome complicating many inflammatory diseases and characterized by fever, pancytopenia, and systemic inflammation. It is clinically similar to hemophagocytic lymphohistiocytosis (HLH), which is caused by viral infection of a host with impaired cellular cytotoxicity. Murine models of MAS and HLH illustrate that interferon-γ (IFNγ) is the driving stimulus for hemophagocytosis and immunopathology. This study was undertaken to investigate the inflammatory contributors to a murine model of Toll-like receptor 9 (TLR-9)-induced fulminant MAS. METHODS Wild-type, transgenic, and cytokine-inhibited mice were treated with an IL-10 receptor blocking antibody and a TLR-9 agonist, and parameters of MAS were evaluated. RESULTS Fulminant MAS was characterized by dramatic elevations in IFNγ, IL-12, and IL-6 levels. Increased serum IFNγ levels were associated with enhanced IFNγ production within some hepatic cell populations but also with decreased numbers of IFNγ-positive cells. Surprisingly, IFNγ-knockout mice developed immunopathology and hemophagocytosis comparable to that seen in wild-type mice. However, IFNγ-knockout mice did not become anemic and had greater numbers of splenic erythroid precursors. IL-12 neutralization phenocopied disease in IFNγ-knockout mice. Interestingly, type I IFNs contributed to the severity of hypercytokinemia and weight loss, but their absence did not otherwise affect MAS manifestations. CONCLUSION These data demonstrate that both fulminant MAS and hemophagocytosis can arise independently of IFNγ, IL-12, or type I IFNs. They also suggest that IFNγ-mediated dyserythropoiesis, not hemophagocytosis, is the dominant cause of anemia in fulminant TLR-9-induced MAS. Thus, our data establish a novel mechanism for the acute anemia of inflammation, but suggest that a variety of triggers can result in hemophagocytic disease.