Features, Treatment, and Outcomes of Macrophage Activation Syndrome in Childhood-Onset Systemic Lupus Erythematosus.

Background Macrophage activation syndrome (MAS) is an uncommon but serious complication of systemic lupus erythematosus (SLE). We aimed to identify factors associated with MAS among adult hospitalized SLE patients. Methods Within the Brigham and Women's Hospital (BWH) Lupus Center Registry, we identified adult SLE patients > age 17 who had been hospitalized from 1970 to 2016, with either ferritin > 5000 ng/ml during admission or "macrophage activation syndrome" or "MAS" in discharge summary. We confirmed MAS by physician diagnosis in medical record review. We matched each hospitalized SLE patient with MAS to four SLE patients hospitalized without MAS (by SLE diagnosis date ±1 year). We employed conditional logistic regression models to identify clinical factors associated with MAS among hospitalized SLE patients. Results Among 2094 patients with confirmed SLE, we identified 23 who had a hospitalization with MAS and compared them to 92 hospitalized without MAS. Cases and controls had similar age at SLE diagnosis (29.0 vs. 30.5, p = 0.60), and hospital admission (43.0 vs. 38.3, p = 0.80), proportion female (78% vs. 84%, p = 0.55), and time between SLE diagnosis and hospitalization (1971 vs. 1732 days, p = 0.84). Arthritis (OR 0.04 (95% CI 0.004-0.35)) and hydroxychloroquine use (OR 0.18 (95% CI 0.04-0.72)) on admission were associated with decreased MAS risk. Admission Systemic Lupus Erythematosus Disease Activity Index scores (30 vs. 19, p = 0.002) and lengths of stay (16 days vs. 3 days, p < 0.0001) were much higher among cases. Death during hospitalization was 19% among cases and 3% among controls ( p = 0.03). Conclusions In this case-control study of hospitalized adult SLE patients, arthritis and hydroxychloroquine use at hospital admission were associated with decreased MAS risk. Further studies are needed to validate these factors associated with lowered MAS risk.

The objective of this study was to describe the clinical and laboratory manifestations, triggers factors, treatment, and outcome of MAS complicating SLE. We retrospectively analyzed the medical records of adult patients with SLE for a period of 8years (2009-2016) and identified patients who had developed MAS. We conducted statistical analysis to identify factors associated with MAS. Among 208 consecutive lupus patients, 20 patients (19 women) were identified having MAS. The mean age of patients was 35.4 ± 10years. MAS revealed lupus in 7 patients. In the others, the delay between diagnosis of SLE and MAS was 33,3months. All cases required hospital admission, and 2 patients were admitted to the intensive care unit. An anemia (hemoglobin < 10g/dL) was found in all patients. A thrombopenia was observed in 19 (95%) cases. Hypertriglyceridemia and hyperferritinemia were present in all patients. All patients had anti-nuclear antibodies and anti-double-stranded DNA antibodies. Bone marrow aspiration showed hemophagocytosis in 15 (94%) cases. The mean SLEDAI was 20.95 corresponding to an SLE of a very high activity. The mean H-Score was 233.85. MAS was associated with a lupus flare in 13 patients. Documented bacterial infections, viral infections, and a breast cancer were respectively diagnosed in 4, 3, and 1 cases respectively. The corticosteroids were administered in all patients. Intravenous cyclophosphamide was used together with corticosteroids in 6 patients, mycophenolate mofetil in 2 cases and azathioprine in 2 cases. Intravenous immunoglobulin was given in 4 cases, etoposide in one case and rituximab was used as the third line treatment in one patient. All infectious episodes were also treated by broad spectrum antibiotics. All patients had a good outcome without any mortality at the management, with a mean follow-up of 24months. The clinical parameters significantly associated with MAS were fever (p = 0,001), splenomegaly (p < 0.0001), lymphadenopathy (p < 0.0001), oral and/or nasopharyngeal ulceration (p = 0.04), arthritis (p = 0.017), and pulmonary signs (p = 0.003). Laboratory parameters associated with MAS were anemia (p < 0.0001), thrombopenia (p < 0.0001), hyperferritinemia (p < 0.0001), hypertriglyceridemia (p < 0.0001), SLEDAI (p < 0.0001), and H-Score (p < 0.0001). Receiver operating characteristic (ROC) analysis identified optimal cutoff values of ferritin (> 695ng/mL) and SLEDAI (> 13.5) to predict the occurrence of MAS in SLE. MAS was observed in 9.62% Moroccan adult patients with SLE. SLE flare and infection were the common triggers of MAS in our study. Our study indicates that the occurrence of unexplained fever, splenomegaly, lymphadenopathy, profound cytopenia, hyperferritinemia, hypertriglyceridemia, high SLEDAI, and H-Score should raises the possibility of the diagnosis of MAS in SLE patients. Early diagnosis and urgent therapeutic management improves the overall prognosis. Key Points • Macrophage activation syndrome (MAS) is an underdiagnosed complication of systemic lupus erythematosus (SLE). The prevalence of this complication in this study is nearly 10%. • The diagnosis of MAS represents a major challenge for clinicians, as it could mimic a SLE flare up or be confused with infections. Validated diagnostic criteria for MAS in adults secondary to SLE are urgently needed. • In this study, the H-score calculate the individual risk of adult patients having reactive MAS. The cut-off value for the H-score was 190.5 (sensitivity 96.7%, specificity 97.6%). • The prognosis of MAS with SLE is good in our study. However, in the literature MAS may be a fatal condition in SLE patients. Prospective studies are necessary to confirm these results.

Macrophage activation syndrome (MAS) is a rare life-threatening complication of rheumatic diseases (RD) that requires early recognition and adequate immediate treatment. Objective of the study: to identify the features of onset of RD in patients who developed MAS, the clinical and laboratory characteristics of the MAS, possible trigger factors and the timing of development. Materials and methods of research: 57 patients (20 boys and 37 girls) with RD who developed MAS were included in a retrospective continuous non-randomized study: 36 (63%) with systemic juvenile idiopathic arthritis (sJIA), 19 (33%) with Systemic lupus erythematosus (SLE), 1 (2%) – with juvenile dermatomyositis (JDM), one (2%) – with overlapping syndrome. Results: in the structure of patients with sJIA, patients with a history of MAS accounted for 28%, among patients with SLE – 7,6%. The median age at the time of sJIA debut in the study group was 2,6 years [1,5; 5,75], patients with SLE – 11,8 years [8,6; 13,95]. The ratio of boys and girls in the study group was 1:1,85. 70 MAS episodes were recorded: 48 – with sJIA, 20 – with SLE, one episode each for JDM and crossover syndrome. A single episode of MAS at the onset had 22% of patients with sJIA, 47% – with SLE, MAS during the course of the disease – 55% and 47%, repeated episodes of MAS – 25% and 5% of patients, respectively. Clinical manifestations of MAS included fever in 91% of children, hepatomegaly in 54%, pericarditis in 51%, skin lesions in 68%, CNS damage in 44%, lung damage in 33%, hyperferritinemia in 96%, thrombocytopenia – in 79%, increased aminotransferases – in 89%, hypertriglyceridemia – in 53%. Patients with sJIA and MAS had statistically significantly earlier onset (p=0,047), a greater number of systemic manifestations (p=0,012), a typical exanthema (p&lt;0,0001), and a smaller number of active joints (p=0,041). 83% of them had episodes of MAS before the initiation of therapy with biological disease-modifying antirheumatic drugs (bDMARDs). There was no statistically significant relationship between the development of MAS with the use of bDMARDs with a clear positive relationship with the violation of the therapy regimen. 19% of patients with sJIA and MAS had a history of infusion reaction to tocilizumab, 8% later had interstitial lung damage. Patients with SLE and MAS at the onset were statistically significantly more likely to have serositis (p=0,0028), ulcers of the oral mucosa (p&lt;0,0001), neuropsychiatric disorders (p=0,0024), positive Coombs' test (p=0,026). All patients received glucocorticoid therapy; experience with the use of GIBP in the study group was limited. Conclusion: MAS in children develops more often with sJIA; the dominant provoking factor is the activity of the underlying disease. The overwhelming majority of patients developed MAS during the course of the disease, less often at the onset. Patients with a history of MAS with sJIA are characterized by an earlier age of onset, a predominance of systemic manifestations, the need for early administration of bDMARDs therapy, and a tendency to infusion reaction to tocilizumab. Against the background of bDMARDs, a subclinical course of MAS with the absence of fever is possible. The risk of developing MAS along with SLE is higher in patients with onset of serositis, ulcers of the oral mucosa, neuropsychiatric disorders, and a positive Coombs' test. MAS cases were detected with high SLE activity at the onset, violation of the treatment protocol.

Macrophage activation syndrome (MAS) is a serious complication of rheumatic diseases. Fever and hyperferritinemia are common in active systemic-onset juvenile idiopathic arthritis (sJIA) and cytopenia in active systemic lupus erythematosus (SLE), thus recognizing MAS in them is a challenge. We compared clinical and laboratory parameters, various classification criteria, and outcomes of MAS in SLE and sJIA. Clinical and laboratory data were extracted from case records of patients with clinician diagnosed cases of SLE-MAS (adult and pediatric) and sJIA-MAS, admitted (2004-2018) at a tertiary care hospital. Ravelli, International consensus, HLH-2004, and criteria proposed by Parodi et al. were applied and compared. Among 33 patients (18 females) with MAS, 19 had SLE (7, childhood-onset SLE) and 14 had sJIA. MAS was more likely to be the presenting manifestation of disease in SLE (p < 0.05). There were no differences in the clinical features among them. Patients with SLE-MAS had lower baseline total leucocyte and platelet counts (p < 0.01), whereas patients with sJIA-MAS had significantly higher median CRP (p = 0.002), fall in TLC (p = 0.012), delta ESR/CRP ratio (p = 0.02), and lower fibrinogen level (p = 0.006). Neutrophil-to-lymphocyte ratio, ferritin/CRP ratio, and the number of patients with ferritin/ESR > 80 were similar. Only 6/33(18%) fulfilled the HLH criteria. Criteria meant for sJIA-MAS or SLE-MAS performed well for both diseases and the majority of patients could be diagnosed using them. Two patients died in each group. MAS in SLE and sJIA is more similar than dissimilar in clinical features and outcome. Criteria meant for MAS in sJIA or SLE-MAS performed equally well in both diseases.

Background There is strong evidence that genetics plays an important role in the pathogenesis of systemic lupus erythematosus (SLE). Genome wide association studies (GWAS) have identified >90 loci associated with SLE risk, which suggests SLE is a complex trait. Yet collectively these genes explain a small fraction of SLE heritability. Within the broad category of SLE, there are genetically distinct Mendelian/monogenic diseases, presenting with lupus features. Macrophage activation syndrome (MAS) is an increasing recognized complication of SLE. It shares similarities with familial hemophagocytic lymphohistiocytosis (HLH), a Mendelian disease. We hypothesize that whole exome (WES) and whole genome sequencing (WGS) of SLE patients suspected of carrying rare genetic variants with large effects, will identify variants and genes associated with SLE risk and MAS. This information has implication for therapy, screening as well as providing insights into the pathogenesis of SLE and MAS broadly. Methods WGS on 8 cSLE patients with one of: (i) age diagnosis Results WGS of cSLE patients revealed potential disease causing monogenic variants in known genes including SLC7A7 and DNASE1 . All MAS-SLE patients heterozygous for ≥1 rare variant in HLH gene, with 5/14 heterozygous for exonic non-synonymous variants in PRF1, LYST, ITK and AP3B1 . Conclusions We identified candidate variants leading to monogenic lupus and MAS in SLE. Additional validation studies are planned to confirm our findings and elucidate the precise pathogenic mechanism leading to disease. These variants have the potential for prognostication, secondary screening of family members and improved therapy for patients and families. Acknowledgements Childhood Arthritis and Rheumatology Research Alliance (CARRA) Small Grant, McLaughlin Centre, University of Toronto.

The clinical presentation of childhood-onset systemic lupus erythematosus (SLE) is generally perceived to differ from that of adult-onset SLE. We aimed to compare the demographic and clinical manifestation between childhood-onset vs. adult-onset SLE in a cohort of Indonesian patients at tertiary care centers. This retrospective study included patients in the Hasan Sadikin Lupus Registry from 2008 until December 2017. The demographics, clinical presentations, and outcomes were compared between childhood-onset SLE (<18years old) (Group 1) and adult-onset SLE (≥18years old) (Group 2). Eight hundred seventy patients were involved into this study. The proportion of childhood-onset SLE was 20% (174 patients). The mean age of group 1 versus group 2 was 13.56 ± 3.04 vs 30.41 ± 8.54years. The following clinical manifestations at SLE diagnosis were significantly more common in childhood-onset than in adult-onset SLE patients: hematological disorder (p = 0.033) and arthritis (p = 0.006). While discoid rash (p = 0.036) and photosensitivity (p < 0.001) were significantly found higher in adult-onset SLE. Cyclophosphamide therapy was significantly more common to be used in childhood-onset (38.5% vs 21.0%, p = <0.001). However, frequency of mortality on follow-up tended to be higher in childhood-onset group (11.5% vs 7.0%, p = 0.208). Arthritis and hematologic involvements at SLE diagnosis were more prominent in childhood-onset compared to adult-onset patients, and mortality in childhood-onset SLE during follow-up relatively higher. This data may suggest the need for more aggressive management approach to childhood-onset patients with SLE.

Remembering Other Causes of Alveolar Siderophages: Macrophage Activation Syndrome

To investigate potential differences between childhood-onset and adult-onset systemic lupus erythematosus (SLE). An inception cohort with childhood-onset SLE (n = 67) was compared with an inception cohort with adult-onset SLE (n = 131), each of whom was diagnosed between 1990 and 1998 and followed up until February 1999. Prospective information included data on medications, laboratory markers, and disease activity and damage as measured by the SLE Disease Activity Index (SLEDAI) and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI), respectively. Eighty-five percent of patients with childhood-onset SLE and 88% of patients with adult-onset SLE were female; the mean duration of followup was 3.2 and 3.5 years, respectively. On average, the children had more-active disease than did the adults at the time of diagnosis and during followup. There was a higher incidence of renal disease in those with childhood-onset SLE (78% versus 52% in adults; P = 0.0005), and the adjusted mean SLEDAI renal score was higher in the children than in the adults (2.37 versus 0.82; P < 0.0001). Treatment with steroids (97% versus 72%; P < 0.0001) and immunosuppressive drugs (66% versus 37%; P = 0.0001) was used significantly more often in children with SLE. Four adult patients with SLE, but none of the children, died during the followup. At the end of the followup, the mean SDI scores in those with childhood-onset SLE were higher than those with adult-onset SLE (1.70 versus 0.76; P = 0.008). Children with childhood-onset SLE have more active disease at presentation and over time than do adults with SLE, especially active renal disease. Compared with adults with SLE, children receive more intensive drug therapy and accrue more damage, often related to steroid toxicity.

BackgroundTo evaluate the impact of macrophage activation syndrome (MAS) on clinical features in patients with Kikuchi-Fujimoto disease (KFD) and to compare the features of MAS in KFD with those of adult-onset Still’s disease (AOSD) and systemic lupus erythematosus (SLE).MethodsThe medical records of febrile patients hospitalised with KFD between November 2005 and April 2017 were reviewed. Patients fulfilling the 2016 classification criteria for MAS were classified as having MAS. Clinical and laboratory features of patients with KFD with and without MAS were evaluated. Poor hospitalisation outcomes were defined as intensive care unit admission or in-hospital mortality. The treatment outcomes of MAS in KFD, AOSD, and SLE were also compared.ResultsAmong 78 patients hospitalised with KFD, 24 (30.8%) patients had MAS during admission. Patients with KFD and MAS more frequently required glucocorticoid treatment (66.7% vs 40.7%, p = 0.036) and had longer hospital stays than patients with KFD without MAS (12.5 vs 8.5 days, p<0.001). In addition, patients with MAS had worse hospitalisation outcomes than patients without MAS (29.2% vs. 0.0%, p<0.001). Among patients with MAS in KFD, AOSD, and SLE, the number of patients requiring glucocorticoid treatment after 3 months was significantly lower among patients with MAS and KFD (KFD 33.3%, AOSD 88.9%, SLE 100%, p<0.001).ConclusionsThe presence of MAS in KFD was associated with adverse clinical outcomes including higher steroid usage and worse hospitalisation outcomes. However, compared to those with AOSD and SLE, patients with MAS and KFD were less likely to require long-term glucocorticoid treatment.

Identifying novel biomarkers for systemic lupus erythematosus associated with macrophage activation syndrome.

Systemic Lupus Erythematosus (SLE) is a common rheumatologic condition with known GI involvement, most notably autoimmune hepatitis and lupus colitis. Acute pancreatitis (AP) is a rare complication of SLE and is typically associated with disease activity. Macrophage activation syndrome (MAS) is an unusual, hyper-inflammatory response to a rheumatologic stimulus characterized by hyperferritinemia, pancytopenia, thermal dysregulation and multiorgan dysfunction. MAS, more commonly seen in children, has been reported to complicate both adult onset SLE and AP. We present a case of necrotizing AP secondary to an SLE flare ultimately complicated by MAS in an adult patient and successfully treated with Anakinra. A 29 year-old female with SLE and non-adherence to medical therapy was admitted with severe necrotizing AP evidenced by epigastric pain, nausea, oral intolerance, lipase >3000 U/L, and CT scan demonstrating necrosis and inflammation in the pancreatic head. After admission, she developed tachycardia, hypothermia, lactate elevation of 17.2, and hypercarbic respiratory failure with pulmonary edema requiring intubation and mechanical ventilation with aggressive supportive care. Laboratory evaluation demonstrated evidence of DIC with pancytopenia, elevated ANA/ds DNA, and a ferritin of 1332 ng/mL. She was started on methylprednisolone for treatment of a SLE flare with clinical improvement leading to extubation. Following extubation, her ferritin level doubled in association with clinical deterioration raising suspicion for MAS. She was then started on Anakinra resulting in brisk clinical response and down trending ferritin. AP occurs in 1-8% of SLE patients and is proposed to be the result of vascular damage. MAS complicates approximately 5.5% of childhood SLE compared to 0.7% of adult SLE but is more commonly the result of AP in combination with SLE compared to SLE alone and is associated with higher mortality rates. Our case uniquely illustrates a rare etiology of AP and the relationship between systemic diseases and the GI system in a critically ill patient. Treatment of MAS is aimed at treating the underlying SLE; however, our patient required the addition of a chemotherapeutic agent. Anakinra is a novel agent which has been used to treat refractory childhood MAS and was successful in treating this adult patient. To the best of our knowledge, this is the only reported case of refractory MAS due to SLE induced AP necessitating treatment with Anakinra.

BackgroundHemophagocytic lymphohistiocytosis (HLH) is characterized by immune dysregulation that results in an uncontrolled hyperinflammatory state. HLH is classified into two main categories: primary (familial) HLH and secondary (acquired) HLH. Secondary HLH can result from various underlying, including infection-associated hemophagocytic syndrome (IAHS) and macrophage activation syndrome (MAS) associated with rheumatologic disorders, among others. Epstein–Barr virus (EBV) often causes IAHS, but central nervous system (CNS) involvement is rare among systemic lupus erythematosus (SLE) patients. We report a case of EBV encephalitis associated with HLH in a patient with childhood-onset SLE.Case presentationA 12-year-old girl had received a diagnosis of SLE 2 months before presentation. After a period of inactive disease on treatment, fever and seizures, with altered mental status and hallucinations, developed over several weeks. A complete blood cell count (CBC) revealed pancytopenia, accompanied by elevated levels of inflammatory markers: 86 mm/hr erythrocyte sedimentation rate, 8.9 mg/dl c-reactive protein, and 3,966 ng/mL of ferritin. The differential diagnosis included active neuropsychiatric SLE, CNS infection and neurological manifestations in secondary HLH, which could have represented either IAHS or MAS. Meropenem and acyclovir were initially administered for clinical acute encephalitis, followed by pulse methylprednisolone; however, the fever persisted, and another CBC revealed progressive cytopenia. A bone marrow study showed hypocellularity and active hemophagocytic activity, and intravenous immunoglobulin was additionally given due to the diagnosis of HLH. Cerebrospinal fluid (CSF) analysis showed 60/mm3 white blood cells (N 55%, L 45%), 141 mg/dL glucose (0.7 blood-CSF glucose ratio), < 4 mg/dL protein; results of Gram stain and bacterial culture were negative. The viral encephalitis panel from the CSF confirmed EBV infection. Bone marrow immunohistochemistry examination revealed increasing levels of CD8 + T-cell and equivocal positive results for EBV-encoded RNA in situ hybridization; therefore, HLH potentially associated with EBV was diagnosed. After treatment with IVIg, cyclosporin A, and prednisolone, the patient’s symptoms gradually improved and she was eventually able to return to school.ConclusionsOur case highlights the importance of a thorough differential diagnosis, including EBV encephalitis associated with HLH, in patients with childhood SLE, particularly in cases of clinical deterioration occurs after initial treatment.

To compare the maternal and fetal outcomes between childhood-onset and adult-onset systemic lupus erythematosus (SLE), we reviewed the medical records of SLE pregnant women treated from January 2005 to August 2013. For comparison, patients were allocated to one of the two groups, those pregnant patients with SLE onset before 18years of age (childhood-onset) and ≥18years (adult-onset). The patients were evaluated at least once in each trimester and postpartum. Relevant maternal and fetal outcomes were extracted, such as lupus flare, preeclampsia/eclampsia, rate of liveborns, fetal loss (spontaneous abortion and stillbirth), term delivery, preterm birth, neonatal death, low birth weight, low birth weight at term, and congenital malformations. We studied 186 pregnancies (in 180 women), 58 of them had childhood-onset SLE, and the remaining 128 had adult-onset SLE. The rate of maternal and fetal complications was similar in both groups. Multivariate analysis showed that active SLE before pregnancy, primigravida, renal flare, preeclampsia, lupus flare, anticardiolipin antibodies, and low serum complement were associated with an increased risk of poor maternal and fetal outcomes. The diagnosis of childhood-onset had no impact on maternal-fetal outcome. The maternal and fetal outcome in women with childhood-onset SLE is similar to that reported in women with adult-onset SLE. Pregnancy in women with childhood-onset SLE should not be contraindicated if the disease is well controlled.

Background Macrophage activation syndrome (MAS) is a severe, potentially life-threatening complication of pediatric rheumatic diseases. MAS occurs most often in children with systemic juvenile idiopathic arthritis (s-JIA) and less commonly in children with systemic lupus erythematosus (SLE), Kawasaki disease (KD) and juvenile dermatomyositis (JDM). The hallmark of MAS includes uncontrolled and dysfunctional immune responses involving continual activation and expansion of T lymphocytes and macrophages, which in turn lead to marked hypercytokinemia. However, it is still unknown which cytokines play a key role in the pathogenesis of MAS among different backgrounds. Objectives This study was aimed to clarify cytokines involved in the development of MAS among different background rheumatic diseases and to identify the serum biomarkers for the diagnosis of MAS. Methods Serum neopterin, interleukin (IL)-18, IL-6, tumor necrosis factor (TNF)-α and soluble TNF receptor type I (sTNFR-I) and sTNFR-II levels were determined using enzyme-linked immunosorbent assay in 112 s-JIA patients including 30 with MAS, 8 SLE patients including 3 with MAS, 67 KD patients including 4 with MAS, and 7 JDM patients including 3 with MAS. Cytokine profiles in MAS phase of each disease were compared to those in active phase. Results Serum neopterin levels in patients with s-JIA, SLE and KD were significantly elevated in MAS phase compared to those in active phase. Serum neopterin levels in patients with JDM were also elevated in MAS phase compared to those in active phase, although statistically significant. Serum sTNFR-I levels in patients with s-JIA and SLE were significantly elevated in MAS phase compared to those in active phase. Serum sTNFR-I levels in patients with KD and JDM were also elevated in MAS phase compared to those in active phase, although statistically significant. Serum sTNFR-II levels in patients with s-JIA and KD were significantly elevated in MAS phase compared to those in active phase. Serum sTNFR-II levels in patients with JDM were also elevated in MAS phase compared to those in active phase, although statistically significant. Serum IL-18 levels in patients with s-JIA were significantly elevated in both active and MAS phase compared to those in patients with other diseases. There were no significant differences of serum IL-6 and TNF-α levels among different backgrounds. Conclusion The elevation of serum neopterin levels was the common finding in patients with MAS even in different backgrounds. These findings indicate that overproduction of interferon (IFN)-γ might be closely related to the development of MAS. Serum neopterin levels which reflect IFN-γ production might be a promising biomarker for the disease activity of MAS.

To clarify the differences and similarities in the cytokine profiles of macrophage activating syndrome (MAS) between systemic lupus erythematosus (SLE) and adult-onset Still's disease (AOSD). The study participants included 9 patients with MAS-SLE, 22 with non-MAS-SLE, 9 with MAS-AOSD, and 13 with non-MAS-AOSD. Serum cytokine levels were measured using a multiplex bead assay. Cytokine levels were compared between patients with SLE and AOSD with/without MAS. Moreover, cytokine patterns were examined using principal component analysis (PCA) and cluster analysis. IL-6, IL-8, IL-18, and TNF-α levels were elevated in patients with SLE and AOSD. IFN-α levels were elevated in SLE, whereas IL-1β and IL-18 levels were elevated in AOSD. In SLE, IFN-α and IL-10 levels were higher in MAS than in non-MAS and controls. PCA revealed distinctive cytokine patterns in SLE and AOSD, SLE with IFN-α and IP-10, AOSD with IL-1β, IL-6, and IL-18, and enhanced cytokine production in MAS. PCA and cluster analysis showed no differences in cytokine patterns between the MAS and non-MAS groups. However, serum ferritin levels were correlated with IFN-α levelsin SLE. Cytokine profiles differed between SLE and AOSD but not between MAS and non-MAS. MAS is induced by the enhancement of underlying cytokine abnormalities rather than by MAS-specific cytokine profiles. Type I IFN may be involved in MAS development in patients with SLE.