Clinical Phenotypes of Adult-Onset Still's Disease: New Insights from Pathophysiology and Literature Findings

Systematic Review and Metaanalysis of Pharmacological Interventions in Adult-Onset Still Disease and the Role of Biologic Disease-Modifying Antirheumatic Drugs

OBJECTIVE

To conduct a systematic review of the effectiveness and safety of pharmacological treatments for adult-onset Still disease (AOSD).

METHODS

Six databases, 2 trial registries, and conference abstracts were searched from January 2012 to February 2023 for studies of pharmacological interventions in people with AOSD. Outcomes were rates of remission and response, discontinuation of concurrent treatments, complications of AOSD, and treatment-related adverse events. Risk of bias was assessed with the Cochrane risk of bias tool and the Joanna Briggs Institute tool for case series.

RESULTS

Forty-four studies evaluated treatments, including nonsteroidal antiinflammatory drugs (NSAIDs), corticosteroids (CS), conventional synthetic disease-modifying antirheumatic drugs (DMARDs), and biologic DMARDs (bDMARDs). For bDMARDs, tocilizumab (TCZ), anakinra (ANK), and canakinumab (CNK) had the most available data. Although 3 randomized controlled trials did not show statistically significant benefits of bDMARDs, metaanalyses showed high rates of complete remission and CS discontinuation. Complete remission was 80% (95% CI 59-92%, I 2 36%), 73% (95% CI 58-84%, I 2 66%), and 77% (95% CI 29-97%, I 2 82%) and CS discontinuation was 57% (95% CI 29-81%, I 2 66%), 47% (95% CI 18-78%, I 2 79%), and 34% (95% CI 6-81%, I 2 59%), respectively, for TCZ, ANK, and CNK. Studies with a higher proportion of patients previously treated with bDMARDs showed a trend toward lower rates of CS discontinuation (P = 0.05). The analyses had high clinical heterogeneity, largely because treatments were prescribed as different lines of therapy.

CONCLUSION

Evidence supports TCZ, ANK, and CNK therapy for AOSD. However, the magnitude of effect and comparative effectiveness of treatments is uncertain.

Recent advances and evolving concepts in Still's disease

Still's disease is a rare inflammatory syndrome that encompasses systemic juvenile idiopathic arthritis and adult-onset Still's disease, both of which can exhibit life-threatening complications, including macrophage activation syndrome (MAS), a secondary form of haemophagocytic lymphohistiocytosis. Genetic insights into Still's disease involve both HLA and non-HLA susceptibility genes, suggesting the involvement of adaptive immune cell-mediated immunity. At the same time, phenotypic evidence indicates the involvement of autoinflammatory processes. Evidence also implicates the type I interferon signature, mechanistic target of rapamycin complex 1 signalling and ferritin in the pathogenesis of Still's disease and MAS. Pathological entities associated with Still's disease include lung disease that could be associated with biologic DMARDs and with the occurrence of MAS. Historically, monophasic, recurrent and persistent Still's disease courses were recognized. Newer proposals of alternative Still's disease clusters could enable better dissection of clinical heterogeneity on the basis of immune cell profiles that could represent diverse endotypes or phases of disease activity. Therapeutically, data on IL-1 and IL-6 antagonism and Janus kinase inhibition suggest the importance of early administration in Still's disease. Furthermore, there is evidence that patients who develop MAS can be treated with IFNγ antagonism. Despite these developments, unmet needs remain that can form the basis for the design of future studies leading to improvement of disease management.

The latest advances in the use of biological DMARDs to treat Still's disease

INTRODUCTION

Currently, the therapeutic management of Still's disease, a multisystemic inflammatory rare disorder, is directed to target the inflammatory symptoms and signs of patients. The treatment varies from glucocorticoids to disease-modifying antirheumatic drugs (DMARDs), both conventional synthetic and biological (bDMARDs). Usually, in refractory patients, bDMARDs are administered.

AREAS COVERED

Among bDMARDs, IL-1 and IL-6 inhibitors are frequently used, as data reported from both clinical trials and 'real-life' experiences. Recently, innovative therapeutic strategies have suggested an early administration of bDMARDs to increase the rate of clinical response and drug-free remission. Some new targets have been also proposed targeting IL-18, IFN-γ, and JAK/STAT pathway, which could be applied to Still's disease and its life-threatening evolution.

EXPERT OPINION

Many lines of evidence improved the knowledge about the therapeutic management of Still's disease with bDMARDs. However, many unmet needs may be still highlighted which could provide the basis to arrange further specific research in increasing the rate of clinical response. In fact, Still's disease remains a highly heterogeneous disease suggesting possible diverse underlying pathogenic mechanisms, at least partially, and consequent different therapeutic strategies. A better patient stratification may help in arranging specific studies to improve the long-term outcome of Still's disease.

Identification of discriminatory factors and construction of nomograms for differentiating AOSD and sepsis

OBJECTIVE

This study aimed to develop nomogram prediction models to differentiate between adult-onset Still's disease (AOSD) and sepsis.

METHODS

We retrospectively collected laboratory test data from 107 hospitalized patients with AOSD and sepsis at the Affiliated Hospital of Xuzhou Medical University. Multivariate binary logistic regression was used to develop nomogram models using arthralgia, WBC, APTT, creatinine, PLT, and ferritin as independent factors. The performance of the model was evaluated by the bootstrap consistency index and calibration curve.

RESULTS

Model 1 had an AUC of 0.98 (95% CI, 0.96-1.00), specificity of 0.98, and sensitivity of 0.94. Model 2 had an AUC of 0.96 (95% CI, 0.93-1.00), specificity of 0.92, and sensitivity of 0.94. The fivefold cross-validation yielded an accuracy (ACC) of 0.92 and a kappa coefficient of 0.83 for Model 1, while for Model 2, the ACC was 0.87 and the kappa coefficient was 0.74.

CONCLUSION

The nomogram models developed in this study are useful tools for differentiating between AOSD and sepsis. Key Points • The differential diagnosis between AOSD and sepsis has always been a challenge • Delayed treatment of AOSD may lead to serious complications • We developed two nomogram models to distinguish AOSD from sepsis, which were not previously reported • Our models can be used to guide clinical practice with good discrimination.

Burden of adult-onset Still's disease: A systematic review of health-related quality of life, utilities, costs and resource use

Adult-onset Still's disease (AOSD) poses a not well estimated burden on patients and healthcare systems. To assess this burden, a systematic review (SR) was undertaken to identify health-related quality of life (HRQoL), utilities, costs and healthcare resource use data. Searches of twelve databases, four conferences, and three key technology assessment and regulatory agency websites were conducted in August 2022. Reference lists of retrieved SRs published since 2017 were also checked. Overall, 16 studies were eligible for inclusion. Eight studies reported HRQoL outcomes, one of which also reported utilities data. Two studies reported direct costs outcomes, and seven reported healthcare resource use data. No indirect costs were identified. A range of outcomes were reported, thus limiting the comparability of results across studies. SF-36 data were impaired in AOSD on most scales, especially those concerning physical activity. Mean SF-36 data were lower across all subscales in patients with active AOSD compared with inactive AOSD. Biologic therapy showed improvements in the SF-36 physical health summary. Utility scores (one study) were significantly lower for AOSD than for healthy controls. Limited direct economic costs data were identified but were substantial where reported. Hospital length of stay ranged from 6.1 to 23.5 days. The SR showed there is a paucity of research reporting the HRQoL and cost burden of AOSD.

Risk of Macrophage Activation Syndrome in Patients with Adult-Onset Still's Disease Treated with IL-1 and IL-6 Inhibitors: A Meta-analysis and Single-Center Experience

INTRODUCTION

Patients with adult-onset Still's disease (AOSD) are at risk of developing macrophage activation syndrome (MAS), a life-threatening condition. Some cases of MAS have been reported following the use of biological agents, highlighting the need to identify contributing factors. This study aims to examine the characteristics of MAS in patients with AOSD treated with anakinra (ANA) or tocilizumab (TCZ).

METHODS

A systematic search was conducted across four online databases to identify studies reporting the incidence rates of MAS in patients with AOSD treated with ANA or TCZ. Meta-analysis was performed using a random-effects model and the generic inverse variance method to estimate the pooled incidence rates. The difference in incidence rates of MAS between TCZ and ANA was assessed. Additionally, we analyzed laboratory data and clinical features of AOSD cases at our institution, stratifying them into two groups: those who developed MAS after TCZ administration and those who did not.

RESULTS

Of the 455 screened articles, we included five ANA and six TCZ studies. The pooled incidence rates of MAS were 1.50% (95% confidence interval [CI], 0-3.36) for ANA (345 patients) and 14.01% (95% CI 4.51-23.51) for TCZ (94 patients). MAS incidence was significantly higher in the TCZ group (P = 0.01). Among the 17 patients from our institution, the six patients who developed MAS had significantly higher white blood cell and neutrophil counts, as well as elevated levels of lactate dehydrogenase, C-reactive protein, and ferritin before TCZ induction (P < 0.05).

CONCLUSIONS

In patients with AOSD, the manifestation of MAS is influenced by multiple causative factors. Consequently, the administration of TCZ should be approached with caution, particularly in patients exhibiting elevated inflammatory markers.

TRIAL REGISTRATION

This study was registered with the Clinical Trial Registry of the University Hospital Medical Information Network (Japan) as UMIN000049243.

Derivation and validation of four patient clusters in Still's disease, results from GIRRCS AOSD-study group and AIDA Network Still Disease Registry

BACKGROUND

Different patient clusters were preliminarily suggested to dissect the clinical heterogeneity in Still's disease. Thus, we aimed at deriving and validating disease clusters in a multicentre, observational, prospective study to stratify these patients.

METHODS

Patients included in GIRRCS AOSD-study group and AIDA Network Still Disease Registry were assessed if variables for cluster analysis were available (age, systemic score, erythrocyte sedimentation rate (ESR), C reactive protein (CRP) and ferritin). K-means algorithm with Euclidean metric and Elbow plot were used to derive an adequate number of clusters.

RESULTS

K-means clustering assessment provided four clusters based on means standardised according to z-scores on 349 patients. All clusters mainly presented fever, skin rash and joint involvement. Cluster 1 was composed by 115 patients distinguished by lower values of age and characterised by skin rash myalgia, sore throat and splenomegaly. Cluster 2 included 128 patients identified by lower levels of ESR, ferritin and systemic score; multiorgan manifestations were less frequently observed. Cluster 3 comprised 31 patients categorised by higher levels of CRP and ferritin, they were characterised by fever and joint involvement. Cluster 4 contained 75 patients derived by higher values of age and systemic score. Myalgia, sore throat, liver involvement and life-threatening complications, leading to a high mortality rate, were observed in these patients.

CONCLUSIONS

Four patient clusters in Still's disease may be recognised by a multidimensional characterisation ('Juvenile/Transitional', 'Uncomplicated', 'Hyperferritinemic' and 'Catastrophic'). Of interest, cluster 4 was burdened by an increased rate of life-threatening complications and mortality, suggesting a more severe patient group.

Clinical characteristics of obese patients with adult-onset Still's disease. Data from a large multicentre cohort

OBJECTIVES

To evaluate the impact of obesity in patients with adult-onset Still's disease (AOSD) and to assess their clinical characteristics and disease outcomes.

METHODS

The clinical features of AOSD patients with a body mass index (BMI)≥30 were assessed among those included in the multicentre Gruppo Italiano di Ricerca in Reumatologia Clinica e Sperimentale (GIRRCS) cohort.

RESULTS

Out of 139 AOSD patients, who had BMI registered in our database, 26 (18.7%) had a BMI≥30. A lower rate of sore throat (P<0.05), pericarditis (P<0.05), and pleuritis (P<0.05) was shown in obese patients. Additionally, obese patients showed higher values of C-reactive protein (CRP) (P<0.05) and ferritin (P<0.05) than others. Furthermore, obese patients were characterised by biologic disease-modifying antirheumatic drug (bDMARD) failure in subsequent follow-up (P<0.05). They also presented higher rate of comorbidity than non-obese patients (P<0.05). Finally, obesity predicted the presence of a chronic disease course in both univariate (HR: 1.72, 95%CI: 1.03-2.51, P<0.05) and multivariate analyses (HR: 1.85, 95%CI: 1.45-2.89, P<0.05). Obesity was also a significant predictor of bDMARD failure in AOSD patients in both univariate (HR: 3.03, 95%CI: 1.42-6.45, P<0.01) and multivariate analyses (HR: 3.59, 95%CI: 1.55-8.27, P<0.01).

CONCLUSION

Obese patients at the time of diagnosis of the disease were characterised by a lower prevalence of sore throat, serositis, as well as by higher values of CRP and ferritin. Obesity was also a predictive factor for a chronic disease course and bDMARD failure, thus highlighting a subset of patients with AOSD to be carefully managed.

Epidemiology, characteristics, treatments, and outcomes of adult-onset Still's disease in Afro-Caribbeans: Results from a population-based study in Martinique, French West Indies

OBJECTIVES

To describe the epidemiology, characteristics, response to initial treatment, and outcomes of Adult-Onset Still's disease (AOSD) in the Afro-Caribbean population of Martinique with free and easy access to specialised care.

METHODS

We conducted a retrospective study from 2004 to 2022 in the island of Martinique, French West-Indies which total population was 354 800 in 2021. Patients were identified from multiple sources including standardised databases. To be included, patients had to be residents of the island and fulfilled Yamaguchi and/or Fautrel's criteria for AOSD, or have a compatible disease course, without a diagnosis of cancer, auto-immune disease or another auto-inflammatory disorder. Date of diagnosis, clinical and biological characteristics, treatments, and outcomes were collected.

RESULTS

The prevalence was 7.6/100 000 inhabitants in 2021. The mean incidence was 0.4/100 000 during study period. Thirty-three patients (70.6% females) with a median follow-up of 35 months [7.5 to 119] were included. Twenty-six patients (78.8%) had a systemic pattern. Patients with a systemic monocyclic pattern had significantly more polyarticular involvement than patients with systemic polycyclic pattern (p = 0.016). Pulmonary involvement occurred in 51.5% of patients at diagnosis and systemic Pouchot score has been identified as an independent predictive factor for pulmonary involvement; OR of 3.29 [CI 95% 1.20; 9.01]. At first flare, all patients but one received oral glucocorticoids, 11 patients (32.4%) received intravenous glucocorticoids pulse and 12 patients (33%) received anti-IL1 therapy. Nineteen patients (57%) relapsed in a median time of 9 months [6 to 12] Three patients (9%) developed hemophagocytosis lymphohistiocytosis, fatal in 1 case. All deceased patients (n = 4, 11.76%) belonged to the systemic polycyclic pattern, with an event-free survival of 13.6 months [IQR 5.7; 29.5] CONCLUSION: AOSD in the Afro-Caribbean population of Martinique shares some similarities with other ethnic groups, but exhibit differences, such as a high proportion of lung involvement. Comparative studies are needed to confirm these results.

Systematic review on the use of biologics in adult-onset still's disease

This systematic review (SR) describes the efficacy and safety of biologic disease modifying anti-rheumatic drugs (bDMARDs) for patients with adult-onset Still's disease (AOSD). Three randomised controlled trials (RCTs), one retrospective case series of multiple interventions, and 17 case series of single interventions met the inclusion criteria for this SR. Comparisons of biologic therapy in AOSD were only available against conventional DMARDs in one RCT and against placebo in two RCTs. There was a lack of common assessment criteria, meaning treatment efficacy across studies could not be compared. Uncontrolled retrospective case series suggested that bDMARDs have an effect for patients with AOSD, but these studies did not provide comparative data to show whether bDMARDs were more effective than other interventions or, whether any bDMARD was more effective than another bDMARD. However, there was evidence that bDMARDs could reduce steroid dose. Safety data from all included studies showed that bDMARDs appear to be a safe alternative to conventional DMARDs. This SR has highlighted the need for larger comparative studies in AOSD and has shown the need to standardize the definition of therapeutic response in AOSD. This would allow comparisons between studies in order to gain clarity on which bDMARDs may be more effective treatments for AOSD.

The Spectrum of Still's Disease: A Comparative Analysis of Phenotypic Forms in a Cohort of 238 Patients

Still's disease (SD) is a heterogeneous autoinflammatory disorder for which several phenotypes have been described. We conducted a retrospective study to re-evaluate the dichotomous view of the disease, to compare the juvenile and adult forms, and to look for prognostic factors. We collected data from ten French centers, seeking patients with a diagnosis of adult-onset SD (AOSD) or systemic juvenile idiopathic arthritis (sJIA). We identified 238 patients, 152 (64%) of whom had AOSD while 86 (36%) had sJIA. The median age at SD onset was 26.6 years. In patients with identifiable patterns, the course of SD was systemic in 159 patients (74%), chronic in 55 (26%). Sore throat and myalgia were more frequent in patients with AOSD. Abnormal liver tests, serum ferritin and C-reactive protein levels were higher in AOSD group. Fever and skin rash were predictive of complete remission or recovery and high lactate dehydrogenase level was a poor prognosis factor. Symptoms such as splenomegaly, skin rash, high polymorphonuclear neutrophils count and macrophage activation syndrome were predictive of a systemic phenotype. Overall, there were no major differences between sJIA and AOSD. Our results are consistent with the "biphasic" model of an autoinflammatory disease that can progress to chronic arthritis if not treated early.

Adult-Onset Still's Disease-A Complex Disease, a Challenging Treatment

Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder with an unknown cause characterized by high-spiking fever, lymphadenopathy, hepatosplenomegaly, hyperferritinemia, and leukocytosis. The clinical course can be divided into three significant patterns, each with a different prognosis: Self-limited or monophasic, intermittent or polycyclic systemic, and chronic articular. Two criteria sets have been validated. The Yamaguchi criteria are the most generally used, although the Fautrel criteria offer the benefit of adding ferritin and glycosylated ferritin values. AOSD's pathogenesis is not yet completely understood. Chemokines and pro-inflammatory cytokines, including interferon (IFN)-γ, tumor necrosis factor α (TNFα), interleukin (IL)-1, IL-6, IL-8, and IL-18, play a crucial role in the progression of illness, resulting in the development of innovative targeted therapeutics. There are no treatment guidelines for AOSD due to its rarity, absence of controlled research, and lack of a standard definition for remission and therapy objectives. Non-steroidal anti-inflammatory drugs (NSAIDs), corticosteroids (CS), and conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) are used in AOSD treatment. Biological therapy, including IL-1, IL-6, IL-18, and IL-17 inhibitors, as well as TNFα or Janus-kinases (JAKs) inhibitors, is administered to patients who do not react to CS and csDMARDs or achieve an inadequate response.

Improving Diagnosis and Clinical Management of Acquired Systemic Autoinflammatory Diseases

Systemic autoinflammatory diseases (SAID) are conditions caused by dysregulation or disturbance of the innate immune system, with neutrophils and macrophages the main effector cells. Although there are now more than 40 distinct, genetically defined SAIDs, the genetic/molecular diagnosis remains unknown for a significant proportion of patients with the disease onset in adulthood. This review focuses on new developments related to acquired/late onset SAID, including phenocopies of monogenic disorders, Schnitzler's syndrome, Adult onset Still's disease, VEXAS syndrome, and autoinflammatory complications associated with myelodysplastic syndrome.

Activation mechanisms of monocytes/macrophages in adult-onset Still disease

Adult onset Still disease (AOSD) is a systemic inflammatory disorder characterized by skin rash, spiking fever, arthritis, sore throat, lymphadenopathy, and hepatosplenomegaly. Although the etiology of this disease has not been fully clarified, both innate and acquired immune responses could contribute to its pathogenesis. Hyperactivation of macrophages and neutrophils along with low activation of natural killer (NK) cells in innate immunity, as well as hyperactivation of Th1 and Th17 cells, whereas low activation of regulatory T cells (Tregs) in acquired immunity are involved in the pathogenic process of AOSD. In innate immunity, activation of monocytes/macrophages might play central roles in the development of AOSD and macrophage activation syndrome (MAS), a severe life-threating complication of AOSD. Regarding the activation mechanisms of monocytes/macrophages in AOSD, in addition to type II interferon (IFN) stimulation, several pathways have recently been identified, such as the pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs)-pattern recognition receptors (PRRs) axis, and neutrophil extracellular traps (NETs)-DNA. These stimulations on monocytes/macrophages cause activation of the nucleotide-binding oligomerization domain, leucine-rich repeat, and pyrin domain (NLRP) 3 inflammasomes, which trigger capase-1 activation, resulting in conversion of pro-IL-1β and pro-IL-18 into mature forms. Thereafter, IL-1β and IL-18 produced by activated monocytes/macrophages contribute to various clinical features in AOSD. We identified placenta-specific 8 (PLAC8) as a specifically increased molecule in monocytes of active AOSD, which correlated with serum levels of CRP, ferritin, IL-1β, and IL-18. Interestingly, PLAC8 could suppress the synthesis of pro-IL-1β and pro-IL-18 via enhanced autophagy; thus, PLAC8 seems to be a regulatory molecule in AOSD. These findings for the activation mechanisms of monocytes/macrophages could shed light on the pathogenesis and development of a novel therapeutic strategy for AOSD.

JAK inhibitors in difficult-to-treat adult-onset Still's disease and systemic-onset juvenile idiopathic arthritis

OBJECTIVES

Excessive and inappropriate production of pro-inflammatory cytokines plays a key role in Still's disease. JAK inhibitor (JAKi) agents mainly block pro-inflammatory cytokine pathways, notably IL-6 and IFN. The objective was to assess the efficacy and safety of JAKi agents in difficult-to-treat systemic juvenile idiopathic arthritis (SJIA) or adult-onset Still's disease (AOSD).

METHODS

This retrospective study was based on a national survey conducted in the departments of rheumatology, paediatric rheumatology and internal medicine of French hospitals regarding SJIA and AOSD patients who received JAKi agents. The data were collected with a standardised questionnaire and analysed at different times (treatment initiation, months 1, 3, and 6 and the end of follow-up).

RESULTS

Nine patients (7 adults) were included. All patients showed inadequate response to corticosteroids or conventional synthetic or biologic disease-modifying anti-rheumatic drugs. Baricitinib was used in 5 patients, ruxolitinib in 2, tofacitinib in 2, and upadacitinib in 1. A JAKi was used combined with corticosteroids in all but 2 patients. A JAKi was associated with anakinra and corticosteroids in one patient, and with methotrexate, anakinra and corticosteroids in another. The median follow-up was 16 [1-33] months. Two cases out 9 showed complete remission, 3/9 partial response and 4/9 treatment failure. At the last visit, corticosteroids could be decreased but not stopped. Tolerance of the JAKi was acceptable (no severe adverse events).

CONCLUSION

JAKi agents may be a therapeutic option for some patients with difficult-to-treat Still's disease, especially those with partial response to medium- or high-dose corticosteroids or biologics.

Adult-Onset Still’s Disease-like Syndrome following COVID-19 Vaccination: A Case Report and Review of the Literature

Adult-onset Still’s disease (AOSD)-like syndrome has rarely been reported as a complication of COVID-19 vaccination. This study reports a 31-year-old female patient who presented with fever, myalgia, arthralgia, pleuropericarditis, leukocytosis, and transaminitis following ChAdOx1 vaccination, and met Yamaguchi’s criteria. A PubMed literature search, performed up until March 2022, identified 10 such cases. A total of 11 cases, including the one in this report, developed AOSD-like syndrome after administration of the viral vector (ChAdOx1) vaccine (six patients) and mRNA vaccine (five patients: BNT162b2 in four and mRNA-1273 in one). There were four male and seven female patients, with their median (Q1, Q3) age and the onset of symptoms after vaccination being 36 years (29, 45) and 10 days (6, 13), respectively. Fever (100%), arthralgia/arthritis (90.9%), skin rashes (81.8%), and sore throat (81.8%) were the main clinical findings. Pericarditis (45.5%), myocarditis/cardiac dysfunction (36.4%), pleuritis (54.6%), and pulmonary infiltrations (36.4%) were also common. One patient developed macrophage activation syndrome. One patient responded well to non-steroidal anti-inflammatory drugs, and the other six showed a good response to high-dose corticosteroids alone. Of the remaining four patients, who showed partial responses to high dose corticosteroids, showed good responses to biological agents. AOSD-like syndrome following COVID-19 vaccination shared many similar clinical features and treatment outcomes to those of idiopathic AOSD (but with a higher prevalence of cardiopulmonary involvement in the former). Physicians should be aware of this extremely rare complication to achieve early diagnosis and provide proper management.

Implications of SARS-CoV-2 Infection in Systemic Juvenile Idiopathic Arthritis

Systemic juvenile idiopathic arthritis (sJIA) is a serious multifactorial autoinflammatory disease with a significant mortality rate due to macrophage activation syndrome (MAS). Recent research has deepened the knowledge about the pathophysiological mechanisms of sJIA-MAS, facilitating new targeted treatments, and biological disease-modifying antirheumatic drugs (bDMARDs), which significantly changed the course of the disease and prognosis. This review highlights that children are less likely to suffer severe COVID-19 infection, but at approximately 2–4 weeks, some cases of multisystem inflammatory syndrome in children (MIS-C) have been reported, with a fulminant course. Previous established treatments for cytokine storm syndrome (CSS) have guided COVID-19 therapeutics. sJIA-MAS is different from severe cases of COVID-19, a unique immune process in which a huge release of cytokines will especially flood the lungs. In this context, MIS-C should be reinterpreted as a special MAS, and long-term protection against SARS-CoV-2 infection can only be provided by the vaccine, but we do not yet have sufficient data. COVID-19 does not appear to have a substantial impact on rheumatic and musculoskeletal diseases (RMDs) activity in children treated with bDMARDs, but the clinical features, severity and outcome in these patients under various drugs are not yet easy to predict. Multicenter randomized controlled trials are still needed to determine when and by what means immunoregulatory products should be administered to patients with sJIA-MAS with a negative corticosteroid response or contraindications, to optimize their health and safety in the COVID era.

Inflammation of Unknown Origin: Evaluation and Prognosis of 57 Cases

(1) Background: there are few studies on the inflammation of unknown origin (IUO). We sought to determine the etiologies and prognosis of IUO, as well as the contribution of complementary examinations. (2) Methods: this retrospective study analyzed patients meeting the Vanderschueren’s criteria in the Hospices Civils de Lyon from 2005 to 2020. (3) Results: a total of 57 patients (mean age: 67 years; interquartile range: 55–79) were included. Final diagnoses were made for 26 (46%) patients. Non-infectious inflammatory diseases were the most common diagnoses (13/26, 50%), followed by neoplasms (10/26, 38%; 8/10 hematological malignancies), infections (2/26, 8%), and miscellaneous causes (1/26, 4%). Moreover, 18-FDG-PET/CT was contributory in 12/42 cases. Anti-neutrophil cytoplasmic antibodies, serology, temporal biopsies, and bone marrow aspirates were contributory in 3/41, 1/57, 5/23, and 3/19 cases, respectively. At last follow-up (mean follow-up duration: 48 months), 8/31 undiagnosed patients were cured (five received an empirical treatment), and 5/31 died (one death was related to the empirical treatment). (4) Conclusion: more than half of the IUO remained undiagnosed. Non-infectious inflammatory diseases and hematological malignancies were the most common etiologies. Moreover, 18-FDG-PET/CT had the highest diagnostic value. Most IUO without final diagnosis persisted. The role of empirical treatments remains to be explored.

The clinical heterogeneity of adult onset Still's disease may underlie different pathogenic mechanisms. Implications for a personalised therapeutic management of these patients

Adult-onset Still's disease (AOSD) is a rare inflammatory disease of unknown aetiology usually affecting young adults and manifesting with a clinical triad of spiking fever, arthritis, and evanescent cutaneous rash. AOSD may be considered a highly heterogeneous disease, despite a similar clinical presentation, the disease course may be completely different. Some patients may have a single episode of the disease whereas others may evolve toward a chronic course and experience life-threatening complications. On these bases, to dissect the clinical heterogeneity of this disease, four different subsets were identified combining the manifestations at the beginning with possible diverse outcomes over time. Each one of these derived subsets would be characterised by a prominent different clinical feature from others, thus proposing dissimilar underlying pathogenic mechanisms, at least partially. Consequently, a distinct management of AOSD may be suggested to appropriately tailor the therapeutic strategy to these patients, according to principles of the precision medicine. These findings would also provide the rationale to recognise a different genetic and molecular profile of patients with AOSD. Taking together these findings, the basis for a precision medicine approach may be suggested in AOSD, which would drive a tailored therapeutic approach in these patients. A better patient stratification may also help in arranging specific designed studies to improve the management of patients with AOSD. Behind these different clinical phenotypes, distinct endotypes of AOSD may be suggested, probably differing in pathogenesis, outcomes, and response to therapies.