Introduction
Adult-onset Still’s disease (AOSD) is an auto-inflammatory disease of unknown etiology, characterized by high fever, transient rash, leukocytosis, arthralgia, and arthritis. The pathogenesis is associated with the overactivation of macrophages and neutrophils by danger signals which activate the inflammasome, leading to the overproduction of pro-inflammatory cytokines [
1]. Although the exact pathogenesis of AOSD remains largely unknown, viral or bacterial infections are considered potential triggers [
2], and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may also be involved as pathogen-associated molecular patterns (PAMPs). With the coronavirus disease 2019 (COVID-19) outbreak, lots of people were infected worldwide. There are significant similarities between AOSD and COVID-19, including a range of clinical and laboratory features such as persistent fever, high serum ferritin, and the tendency to develop cytokine release syndrome [
3]. The activation of NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) was important in both diseases [
1,
4]. There have been several case reports of AOSD following SARS-CoV-2 infection and vaccination [
5,
6]. Thus, the excessive inflammatory responses that occur in patients with AOSD and patients with severe COVID-19 may share similar mechanisms.
In December 2022, following a change in relevant prevention policies in China, the population had a concentration of infections, mainly with the Omicron strain. Although several previous studies have assessed the effects of SARS-CoV-2 infection in rheumatic diseases, data from patients with AOSD are limited and it is unclear which risk factors are associated with severe outcomes of COVID-19 in this population. Following this outbreak of COVID-19, we retrospectively collected and analyzed clinical data on COVID-19 in patients with AOSD up to March 15, 2023. Our study aimed to describe the factors associated with COVID-19 severity in patients with AOSD and assess the impact of COVID-19 on disease activity.
Patients and Methods
Study Design and Population
We conducted a retrospective observational cohort study among patients with AOSD under long-term outpatient follow-up at the Department of Rheumatology and Immunology, Ruijin Hospital, China. The patients were diagnosed with AOSD according to the Yamaguchi criteria. The study was conducted between December 15, 2022 and March 15, 2023. As a result of the COVID-19 pandemic, patient data collection was conducted remotely using internet-based methods. Reputable online platforms and telecommunication tools were used to establish contact with patients and obtain their clinical information. Informed consent was obtained electronically, with detailed explanations of the study purpose, procedures, and confidentiality measures provided. Secure online data collection instruments, including web-based questionnaires and electronic medical record forms, were designed to capture relevant information while ensuring data reliability and accuracy. This study was approved by the Institutional Research Ethics Committee of Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, China with Institutional Review Board number KY2022-182, and was performed in compliance with the Declaration of Helsinki with written informed consent from the subjects.
Data Collection
Demographic data, clinical characteristics, treatments, and outcomes were collected. COVID-19 was confirmed as positive for SARS-CoV-2 by polymerase chain reaction (PCR) or antigen. COVID-19 was suspected if patients reported associated symptoms (new onset of fever and presence of at least one respiratory symptom) and a history of epidemiological exposure. Symptoms collected for COVID-19 included fever, sore throat, cough, expectoration, nasal congestion, runny nose, dyspnea, diarrhea, anosmia or ageusia, muscle soreness, conjunctivitis, and fatigue. The severity of COVID-19 was classified as mild (did not or mildly interfered with daily activity), moderate (severely interfered with daily activity), or severe (required urgent medical attention or hospitalized medications). Medium or high-dose oral glucocorticoids were defined as more than 7.5 mg/day [
7].
The definition of AOSD flare includes the presence of at least two AOSD-related symptoms together with elevated levels of inflammatory indicators such as C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and ferritin and requiring medication adjustment [
8]. The AOSD flare within 3 months after the infection of SARS-CoV-2 was considered a post-infection disease flare. The systemic score was assessed in all patients with disease flares. The score included 12 items: fever, typical rash, pleuritis, pneumonia, pericarditis, hepatomegaly or abnormal liver function tests, splenomegaly, lymphadenopathy, leukocytosis of more than 15,000/mm
3, sore throat, myalgia, and abdominal pain.
Statistical Analysis
Medians (with interquartile range) or mean (with standard deviation) for continuous variables and frequencies (with proportions) for categorical variables were presented. Baseline characteristics and medication were summarized and stratified by COVID-19 severity. The relationship between each risk factor (comorbidities, vaccination, and medicine use) and COVID-19 severity was further assessed using logistic regression models after adjusting by age, gender, and body mass index (BMI). Binary covariates with a total sample size less than 5 were not included. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were reported. A two-sided p value less than 0.05 was considered statistically significant. All analyses were performed using SPSS software (version 26.0).
Discussion
Since the beginning of December 2022, following a relevant policy change in China, there has been a large outbreak of SARS-CoV-2 infection, predominantly with the Omicron strain [
10]. The COVID-19 epidemic has significantly influenced patients with rheumatic diseases, and patients with AOSD are no exception. The present study analyzed the clinical characteristics of patients with AOSD and COVID-19 and the impact of various factors on the prognosis of the infectious process.
The infection rate of SARS-CoV-2 in patients with AOSD was 75.5%, including patients with confirmed and highly suspected COVID-19, consistent with the general population (63.52% confirmed rate up to 25 December 2022) [
9]. Of note, the infection rate might be underestimated, because some patients might be asymptomatic. Among all patients with AOSD with confirmed or suspected COVID-19, the COVID-19-related hospitalization rate was 4.9% (7 out of 142) and the mortality rate was 0.7% (1 out of 142). Given the low hospitalization rate in our study, extrapolation to the general population is challenging, although previous data showed similar critical or mortality rates (533 of 48,234 [1.1%]) [
11]. Remarkably, the shortage of medical resources due to this large outbreak in a short period may have prevented the hospitalization of some patients with COVID-19, resulting in a lower hospitalization rate. The cause of death in one patient was considered to be severe HLH, one of the most serious complications of AOSD. However, it is challenging to determine whether the cause of her death was the onset of COVID-19, the flare of AOSD, or a combination of both. Additionally, the COVID-19 probably worsened her pulmonary hypertension. Similarly, patients with severe COVID-19 may also develop secondary HLH, which usually occurs in patients presenting with acute respiratory distress syndrome (ARDS) [
12]. The HLH of this patient might be secondary to AOSD because the pneumonia was not severe.
The patients with AOSD in this study received mainly inactivated SARS-CoV-2 vaccines, and our previous study has shown that inactivated vaccines did not cause disease relapse in clinically inactive patients with AOSD and that adverse effects were mild and self-limiting [
13]; however, the efficacy of inactivated vaccines is unclear. Following logistic regression analysis of risk factors for COVID-19 severity, although no statistical difference was reached, it was found that vaccination may result in a superior outcome for patients, consistent with the findings in the general population [
11] and other populations with rheumatic diseases [
14], but our conclusion requires further validation. Possible reasons include the long interval between vaccination and infection, and the suppression of the immunogenicity of the vaccine due to the use of immunosuppressive drugs or glucocorticoids, which requires further validation. In addition, not surprisingly, age and the presence of comorbidities (COPD or asthma and possible hypertension) increase the risk of deterioration of COVID-19 in patients with AOSD, which is consistent with the previous studies.
In terms of medication use, medium or high-dose oral glucocorticoids (> 7.5 mg/day) were associated with more severe COVID-19, which is concordant with data from patients with other rheumatic diseases [
15‐
17]. The mechanisms involved have not been fully elucidated, but this is not surprising since glucocorticoids are comprehensive inhibitors of the host inflammatory response to defend against the virus. Moreover, patients on medium or high-dose glucocorticoids may still have immune dysregulation which contributes to the worse outcome of COVID-19. Although hydroxychloroquine was originally proposed as a therapeutic agent for COVID-19, it was not shown to be protective in preventing adverse patient outcomes in our cohort, in line with previous reports on patients with rheumatic diseases [
17], including systemic lupus erythematosus (SLE) [
18]. The use of JAK inhibitors is strongly associated with an adverse prognosis of COVID-19 in patients with rheumatic diseases [
15,
19], and similar to previous studies, we found that patients receiving JAK inhibitors had a worse outcome. While caution is needed in drawing this conclusion since the number of patients using JAK inhibitors in our study was so small. However, one study found that baricitinib reduced mortality in patients hospitalized for COVID-19 [
20]. This may be related to the timing of drug use, where baseline use of JAK inhibitor at the initial phase of SARS-CoV-2 infection may suppress the immune response against the virus, whereas initiation of JAK inhibitor at the time of clinical deterioration may attenuate the abnormal systemic inflammatory response.
Our study identified six patients with AOSD suffering from AOSD flares within 3 months of SARS-CoV-2 infection, four of whom were hospitalized and one died, suggesting that SARS-CoV-2 might cause flares of AOSD. During the follow-up period, no disease flares were reported in patients with AOSD without COVID-19, and there was no statistical difference compared to patients with COVID-19 (
p = 0.339). A case of AOSD onset after COVID-19 has been reported previously [
5]. The potential pathogenic role of various pathogens in AOSD, particularly viruses, has attracted extensive attention. The formation of a cytokine storm is the key to the pathogenesis of AOSD. The starting point of the cytokine storm may arise from specific viral danger signals. Both severe COVID-19 and AOSD can be grouped as hyperferritinemia syndrome, share the same clinical features of high inflammation and cytokine storm, and possibly have the same molecular mechanisms [
21]. Studies have shown that ferritin induces NETs (neutrophil extracellular traps) release and promotes systemic inflammation in AOSD [
22], and a ferritin–NETs–cytokine storm loop may also be present in COVID-19 due to the formation of NETs and hyperferritinemia syndrome which are characteristic of patients with severe COVID-19. A potentially faulty immune response against SARS-CoV-2 may have triggered AOSD in patients.
This is the first study to evaluate the impact of COVID-19 in patients with AOSD and, as a result of a short-term outbreak of COVID-19, participants were infected with a similar strain of SARS-CoV-2. However, there are limitations. First, because of the rareness of the disease, the sample size was limited. In addition, owing to the retrospective observational study setting, unmeasured confounding factors may affect the results.