Kawasaki Disease and Multisystem Inflammatory Syndrome in Children: common inflammatory pathways of two distinct diseases

Differentiating Kawasaki Disease and Multisystem Inflammatory Syndrome in Children Using Blood Composite Scores: Insights into Clinical Outcomes and Predictive Indices

The study sought to assess the clinical utility of complete blood count-derived composite scores, suggesting their potential as markers of inflammation and disease severity in Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) with Kawasaki-like features. This retrospective study analyzed data from 71 KD and 73 MIS-C patients and 70 healthy controls. The KD group showed a higher rate of coronary involvement (26.7% vs. 10.9%), while the MIS-C group had a higher intensive care unit (ICU) admission rate (34.2% vs. 2.8%). Platelet counts, lymphocyte counts, mean platelet volume (MPV), MPV/Lymphocyte (MPVLR), and MPV/Platelet (MPVPR) ratios demonstrated the highest specificities in distinguishing MIS-C than KD (84.5%, 83.1%, 91.1%, 88.7%, and 88.7%, respectively). Monocyte counts, MPV, and MPVPR demonstrated the highest specificities to predictive ICU admission in the MIS-C group (83.3%, 89.6%, and 89.6%, respectively). Lymphocyte counts, platelet/lymphocyte ratio (PLR), neutrophil/lymphocyte ratio (NLR), MPVLR, and Systemic Immune-Inflammation Index (SII) parameters were found to have high negative predictive values for predicting KD patients without coronary artery lesions (CALs) (85.7%, 86.1%, 87.1%, 87.1%, and 85.7%, respectively)., Systemic Inflammation Response Index (SIRI), MPVPR, and CRP were independently predictive of ICU admission in the MIS-C group, and lymphocyte count and IVIG resistance were also identified as significant predictors of CALs in the KD group. NLR, MPVLR, MPVPR, and NPR indices effectively differentiate MIS-C from KD and predict ICU admission in MIS-C. NLR, PLR, MPVLR, and SII are valuable in excluding CALs in KD with high negative predictive values. In addition, SIRI and MPVLR were independent predictors of ICU admission in MIS-C, and lymphocyte count was identified as an independent predictor of CALs in KD.

Advancing multidisciplinary management of pediatric hyperinflammatory disorders

Pediatric hyperinflammatory diseases, including Still's disease, Kawasaki disease (KD), multisystem inflammatory syndrome in children (MIS-C), and recurrent pericarditis (RP), represent a spectrum of conditions characterized by immune dysregulation and systemic inflammation. Each disorder exhibits distinct pathophysiological mechanisms and clinical features, yet their overlapping presentations often pose diagnostic challenges. Early and accurate differentiation is critical to mitigate complications such as macrophage activation syndrome (MAS), coronary artery aneurysms, and myocardial dysfunction. This narrative review explores the pathophysiology, diagnostic criteria, and management of these conditions, emphasizing the utility of advanced biomarkers, imaging modalities, and genetic testing. For Still's disease, the review highlights the transformative role of biologic therapies targeting IL-1 and IL-6 in reducing systemic inflammation and improving outcomes. In KD, timely administration of intravenous immunoglobulin (IVIG) and combination with high-dose steroids in high-risk patients is pivotal for preventing coronary complications. MIS-C, associated with SARS-CoV-2 infection, requires tailored immunomodulatory approaches, including corticosteroids and biologics, to address severe hyperinflammation and multiorgan involvement. RP management prioritizes NSAIDs, colchicine, and IL-1 inhibitors to reduce recurrence and corticosteroid dependence. The review advocates for a multidisciplinary approach, integrating standardized diagnostic algorithms and disease-specific expertise to optimize patient care. Future research directions include the identification of predictive biomarkers, exploration of novel therapeutic targets, and development of evidence-based treatment protocols to enhance long-term outcomes in pediatric inflammatory diseases.

Multisystem inflammatory syndrome in children and Kawasaki disease

This narrative review aims to analyze and compare the current literature on multisystem inflammatory syndrome in children (MIS-C) and Kawasaki disease (KD), with a focus on case definitions, clinical features, diagnostic approaches, treatment strategies, and outcomes. Through a comprehensive review of relevant studies, including screening titles, abstracts, and full-text articles, key similarities and differences were identified. Both MIS-C and KD involve immune system dysregulation and share clinical manifestations such as rash, gastrointestinal symptoms, and cardiovascular involvement, with treatments often centered around immunomodulatory therapies. However, significant differences were observed, particularly in terms of age distribution, demographic prevalence, clinical presentation, and diagnostic criteria, with KD primarily affecting younger children and being associated more prominently with coronary artery abnormalities. While both diseases raise concerns about severe cardiac involvement and the need for intensive care, their pathogenic mechanisms have not been fully understood. Ongoing research is critical to elucidating these mechanisms, refining diagnostic criteria, and optimizing therapeutic approaches to improve outcomes for affected children. This comparative analysis is essential for advancing the understanding of both conditions, as accurately distinguishing between MIS-C and KD has significant implications for clinical decision-making and patient management. Given their overlapping yet distinct clinical features, precise differentiation is critical for ensuring timely diagnosis, optimizing therapeutic strategies, and improving patient outcomes. The concern among pediatric patients stems from the potential for severe complications, particularly cardiac involvement, which underscores the need for heightened awareness, early recognition, and evidence-based treatment strategies to minimize long-term morbidity and mortality.

Contemporary Diagnosis, Management, and Early Outcomes in Children with Kawasaki Disease in Romania: A Single-Center Experience

Background: Kawasaki disease (KD) is an acute inflammatory vasculitis with a particularly high incidence of coronary artery complications and constitutes a significant cause of acquired heart disease in children and young adults. Methods: We conducted a retrospective analysis of consecutive patients aged 0-18 years hospitalized at the "Prof. Dr. Matei Balş" National Institute of Infectious Diseases in Bucharest with Kawasaki disease over a period of 6 years (2018-2023). Results: A total of 25 children were discharged from hospital with this diagnosis during the analyzed period. The mean age was 2.9 years, and 56% were boys. Fever ≥5 days was present in all cases, and the most frequent additional sign was the presence of oral changes. Patients were treated according to in-effect guidelines with intravenous immunoglobulin (IVIG) (100%) and acetylsalicylic acid (68%). Only two cases were considered IVIG resistant and received a second IVIG infusion. Only mild cardiovascular changes were noted in echocardiography: mild coronary artery dilatation (21.7% of cases), mild valvular regurgitation, and small pericardial effusion. Infants displayed less inflammation and higher percentages of leukocytosis, developed an increase in platelet count sooner, received IVIG faster, and had longer hospital stays. Outcomes were generally favorable, and 92% of children were discharged, while the two remaining patients were transferred to other centers. No deaths were recorded. Conclusions: To our knowledge, this is the largest contemporary Romanian cohort of Kawasaki disease published to date, outlining the local diagnostic process, therapeutic strategies, and early outcomes of Kawasaki disease.

Comparison of methylprednisolone alone versus intravenous immunoglobulin plus methylprednisolone for multisystem inflammatory syndrome in children (MIS-C)

BACKGROUND

As a first-line therapeutic option for multisystem inflammatory syndrome in children (MIS-C) with surging demand, intravenous immunoglobulin (IVIG) is associated with escalating costs and supply shortages, particularly in low-income and middle-income countries. This study compares the effectiveness of methylprednisolone alone versus IVIG combined with methylprednisolone for managing MIS-C.

METHODS

We conducted a retrospective cohort study from January 2022 to June 2023 at Vietnam National Children's Hospital. We used propensity score matching to compare the short-term outcomes based on immunomodulatory therapy with methylprednisolone alone or IVIG plus methylprednisolone.

RESULTS

We included 391 patients, comprising 255 boys and 136 girls, who fulfilled the MIS-C case definition of the US Centers for Disease Control and Prevention. Most patients (80.8%) received intravenous methylprednisolone monotherapy, and 19.2% were administered IVIG in addition to methylprednisolone. In general, the laboratory values indicative of hyperinflammatory and hyperthrombotic states displayed significant early response within 2-3 days after initial treatment, including white cell count (SE=1.77, p<0.001), NEU (SE=0.76, p=0.03), C reactive protein (SE=-46.51, p<0.001), PLT (SE=38.05, p=0.002), fibrinogen (SE=-0.37, p=0.002), d-dimer (SE=-849.8, p=0.02)); while subsequent improvement in cardiac markers was also observed, with pro-B-type natriuretic peptide (SE=-165.2, p<0.001) on day 5 and troponin I (SE=-0.05, p=0.004) on day 7. After propensity score weighting, there were 41 patients in each treatment group. Notably, there were no significant differences in the incidence of cardiac events between treatment groups regarding left ventricular dysfunction and coronary artery dilation or aneurysms (10.3% vs 20.7%, p=0.074 and 63.4% vs 56.1%, p=0.653, respectively). While the median paediatric intensive care unit length of stay (LOS) and hospital LOS were slightly lengthier in the IVIG and methylprednisolone group compared with those of the methylprednisolone group, these differences were not statistically significant ((5 vs 4, p=0.782) and (9 vs 7, p=0.725), respectively).

CONCLUSIONS

Initial treatment with methylprednisolone monotherapy appears not inferior in effectiveness to adjunctive IVIG plus methylprednisolone in MIS-C. Further investigations in randomised controlled trials deserve to be undergone to clarify if IVIG-sparing glucocorticoids are a viable option for achieving favourable outcomes in MIS-C, particularly in resource-limited settings with barriers approaching IVIG therapy.

Coronary artery dilation in children with MIS-C: prevalence, risk factor, and progression

Cardiac injury is the critical issue in children with MIS-C, particularly coronary artery dilation. This study aimed to describe the prevalence, risk factors associated with coronary artery abnormalities, and their progression after 3 months of follow-up in MIS-C children in Vietnam. A prospective multicenter case series study was conducted on MIS-C patients diagnosed per WHO criteria from September 2021 to February 2023 at the two largest pediatric hospitals in southern Vietnam. Data on demographics, clinical features, laboratory findings, and treatments during the acute phase of MIS-C were collected. Patients were followed for 3 months post-discharge and categorized into normal and abnormal coronary artery groups for comparative analysis. Among 195 patients (mean age 6.3 years; male to female ratio 1.5:1), 33.3% exhibited coronary artery abnormalities at admission. Treatment included a combination of intravenous immunoglobulin (IVIG) and corticosteroids (53.3%), corticosteroids alone (42.6%), and IVIG alone (4.1%). After 3 months, only 3.6% of patients had persistent coronary artery abnormalities. Independent risk factors for coronary artery dilation included male sex (OR 4.59; 95% CI 1.62-12.94; p = 0.004), Kawasaki-like phenotype (OR 6.42; 95% CI 2.25-18.33; p = 0.001), and mesenteric lymphadenitis (OR 8.79; 95% CI 1.74-44.31; p = 0.008).

CONCLUSION

Coronary artery dilation in MIS-C patients shows a favorable recovery trajectory after a 3-month follow-up. Male sex, Kawasaki-like MIS-C, and mesenteric lymphadenitis are independent risk factors for coronary artery dilation in MIS-C patients.

WHAT IS KNOWN

• Multisystem inflammatory syndrome in children (MIS-C) is a severe inflammatory syndrome following SARS-CoV-2 infection, often leading to cardiac complications, particularly coronary artery dilation.

WHAT IS NEW

• Coronary artery dilation in MIS-C patients mostly resolves within three months of follow-up. Factors associated with coronary artery dilation in MIS-C patients include: male sex, Kawasaki-like phenotype and mesenteric lymphadenitis.

Development of Preliminary Criteria of Macrophage Activation Syndrome in Multisystem Inflammatory Syndrome Associated with COVID-19 in Children

Background: Macrophage activation syndrome (MAS) can be regarded as a key factor determining the severity of multisystem inflammatory syndrome associated with COVID-19 in children (MIS-C), and often requires treatment in the intensive care unit (ICU) to avoid life-threatening complications. No reputable specific criteria for the diagnosis of MAS in MIS-C patients have yet been identified, and criteria currently used for the diagnosis of hemophagocytic syndromes, such as HLH-2004, MAS-2005, and MAS-2016, are not sufficient for MAS in MIS-C. Our goal in this study was to work out the criteria for the early diagnosis of MAS in MIS-C. Methods: One hundred and sixty-six (166) patients with MIS-C were assessed retrospectively. The two most experienced experts independently identified patients with MAS. The patients were divided into three cohorts: MAS (n = 19), without MAS (n = 78), and probable MAS (n = 67). The latter included patients diagnosed with MAS by only one expert, and it was excluded from the analysis. Results: The age of patients with MAS was much higher, and they more frequently had edematous syndrome, hypotension and/or shock, splenomegaly, and CNS involvement. In their blood tests, thrombocytopenia, hypoalbuminemia, and hypertriglyceridemia occurred more often. The level of biomarkers of inflammation, such as ferritin, CRP, troponin, AST, and ALT, was also higher in this group. Increased fibrinogen and D-dimer were also found, demonstrating hypercoagulation in the MAS-MIS-C group. We chose 21 continuous and categorical variables with statistical significance, out of which 2-ferritin > 469 μg/L or platelets < 114 × 109/L-allowed us to discriminate MAS patients. Conclusions: Ferritin > 469 μg/L or platelets < 114 × 109/L can be regarded as key signs to differentiate MAS in MIS-C patients with a sensitivity of 100% and specificity of 94.9%, and they can be used along with other diagnostic methods.

Heterozygous BTNL8 variants in individuals with multisystem inflammatory syndrome in children (MIS-C)

Multisystem inflammatory syndrome in children (MIS-C) is a rare condition following SARS-CoV-2 infection associated with intestinal manifestations. Genetic predisposition, including inborn errors of the OAS-RNAseL pathway, has been reported. We sequenced 154 MIS-C patients and utilized a novel statistical framework of gene burden analysis, "burdenMC," which identified an enrichment for rare predicted-deleterious variants in BTNL8 (OR = 4.2, 95% CI: 3.5-5.3, P < 10-6). BTNL8 encodes an intestinal epithelial regulator of Vγ4+γδ T cells implicated in regulating gut homeostasis. Enrichment was exclusive to MIS-C, being absent in patients with COVID-19 or bacterial disease. Using an available functional test for BTNL8, rare variants from a larger cohort of MIS-C patients (n = 835) were tested which identified eight variants in 18 patients (2.2%) with impaired engagement of Vγ4+γδ T cells. Most of these variants were in the B30.2 domain of BTNL8 implicated in sensing epithelial cell status. These findings were associated with altered intestinal permeability, suggesting a possible link between disrupted gut homeostasis and MIS-C-associated enteropathy triggered by SARS-CoV-2.

Multisystem Inflammatory Syndrome in Children Versus Neonates: A Case Series

After several reports of a multisystem inflammatory disease in pediatric patients who had evidence of active or past infection with the novel coronavirus SARS-CoV-2, in May 2020, the Centers for Disease Control and Prevention (CDC) provided a case definition for this multisystem inflammatory syndrome in children (MIS-C). A similar presentation in neonates has been termed multisystem inflammatory syndrome in neonates (MIS-N). There is considerable overlap between clinical presentation for MIS-C and Kawasaki disease (KD) or atypical KD. Early diagnosis and treatment of these conditions are crucial to prevent serious complications. This case series describes three cases of MIS-C and MIS-N each and aims to provide evidence to advance the current understanding of these conditions.

The Central Role of Interleukin-1 Signalling in the Pathogenesis of Kawasaki Disease Vasculitis: Path to Translation

Kawasaki disease (KD) manifests as an acute febrile condition and systemic vasculitis, the etiology of which remains elusive. Primarily affecting children under 5 years of age, if untreated KD can lead to a significant risk of coronary artery aneurysms and subsequent long-term cardiovascular sequelae, including myocardial ischemia and myocardial infarction. Intravenous immunoglobulin therapy mitigates the risk of aneurysm formation, but a subset of patients exhibit resistance to this treatment, increasing the susceptibility of coronary artery lesions. Furthermore, the absence of a KD-specific diagnostic test or biomarkers complicates early detection and appropriate treatment. Experimental murine models of KD vasculitis have substantially improved our understanding of the disease pathophysiology, revealing the key roles of the NLRP3 inflammasome and interleukin-1 (IL-1) signalling pathway. This review aims to delineate the pathophysiologic findings of KD while summarising the findings for the emerging key role of IL-1β in its pathogenesis, derived from both human data and experimental murine models, and the translational potential of these findings for anti-IL-1 therapies for children with KD.

NK Cell and Monocyte Dysfunction in Multisystem Inflammatory Syndrome in Children

Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infection characterized by multiorgan involvement and inflammation. Testing of cellular function ex vivo to understand the aberrant immune response in MIS-C is limited. Despite strong Ab production in MIS-C, SARS-CoV-2 nucleic acid testing can remain positive for 4-6 wk postinfection. Therefore, we hypothesized that dysfunctional cell-mediated Ab responses downstream of Ab production may be responsible for delayed clearance of viral products in MIS-C. In MIS-C, monocytes were hyperfunctional for phagocytosis and cytokine production, whereas NK cells were hypofunctional for both killing and cytokine production. The decreased NK cell cytotoxicity correlated with an NK exhaustion marker signature and systemic IL-6 levels. Potentially providing a therapeutic option, cellular engagers of CD16 and SARS-CoV-2 proteins were found to rescue NK cell function in vitro. Taken together, our results reveal dysregulation in Ab-mediated cellular responses of myeloid and NK cells that likely contribute to the immune pathology of this disease.

Characteristics of Multisystem Inflammatory Syndrome in Children Across COVID-19 Variants in Vojvodina

Background/Objectives: To investigate if the severity and presentation of multisystem inflammatory syndrome in children (MIS-C) vary between different severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants. Methods: This retrospective study included 59 patients aged 0-18 years, diagnosed with COVID-19 and MIS-C, treated and monitored over a one-year period after discharge from hospital. The patients were grouped according to the predominant SARS-CoV-2 variant. The predominant variant of SARS-CoV-2 was assumed by the date of hospitalization. The following patient data were collected: demographic data (age, sex), information on comorbidities, body mass index, clinical data (fever and duration of febrile periods, symptoms of Kawasaki-like phenotypes, and presence of respiratory, cardiovascular, gastrointestinal, neurological and other symptoms), and laboratory and imaging findings. Results: In total, 24 (41%), 19 (32%), and 15 (25%) patients were diagnosed with MIS-C during the Alpha, Delta, and Omicron periods, respectively (63.8% were males; 36.2% were females). Comorbidities were present in 49% of patients. Respiratory symptoms were the most common during the Delta period (73%, p = 0.028). There was no statistically significant difference in the occurrence of other symptoms, laboratory findings, treatment, complications, and long-term outcomes between groups. Conclusions: No significant correlation was found between hospitalization date (used to estimate COVID-19 variant) and presentation/severity of MIS-C.

A Comparison of Kawasaki Disease during the SARS-CoV-2 Pandemic with Multisystem Inflammatory Syndrome in Children

OBJECTIVES

The purpose of this study was to compare and contrast Kawasaki disease (KD) with multisystem inflammatory syndrome in children (MIS-C) during the SARS-CoV-2 pandemic.

METHODS

A retrospective analysis of the medical records of patients diagnosed with KD and MIS-C at a single institution from July 2020 to November 2021 was performed.

RESULTS

The study included 39 MIS-C patients (84.6% male) with a median age of 138 months and 17 KD patients (58.8% male) with a median age of 36 months. The MIS-C patients were older (p < 0.001) and had prolonged hospitalizations (p = 0.023), elevated neutrophil counts (p < 0.001), C-reactive protein (p < 0.001), procalcitonin (p < 0.001), interleukin-6 (p < 0.014), ferritin (p < 0.001), fibrinogen (p < 0.001), troponin I (p = 0.001), NT-proBNP (p < 0.001), and D-dimer levels (p < 0.001). There were more cases of hypotension (p = 0.024), decreased left ventricular function (p = 0.023), and a greater need for corticosteroids (p < 0.001), enoxaparin (p = 0.045), and therapeutic plasma exchange (p < 0.001). Kawasaki disease patients had a greater incidence of rash (p < 0.001), changes in oral mucosa (p < 0.001), conjunctival injection (p < 0.001), extremity changes (p < 0.001), and cervical lymphadenopathy (p < 0.001). They had a longer duration of fever (p < 0.001), elevated white blood cell count (p < 0.001), platelet count (p < 0.001), and alanine aminotransferase level (p < 0.001). The two groups were similar regarding the hemoglobin levels, erythrocyte sedimentation rates, albumin levels, and the frequency of coronary aneurysm, myocarditis, pericarditis, invasive mechanical ventilatory support, and intravenous immunoglobulin treatment.

CONCLUSIONS

Advanced patient age, a greater presence of gastrointestinal and cardiac findings associated with hypotension, increased NT-proBNP levels, decreased left ventricular function, the use of various treatment modalities, and longer hospital stays suggest MIS-C, whereas prolonged fever and classical clinical features of KD favor KD.

Proteomic Signatures of Multisystem Inflammatory Syndrome in Children (MIS-C) Associated with COVID-19: A Narrative Review

BACKGROUND/OBJECTIVES

Multisystem Inflammatory Syndrome in Children (MIS-C) is a post-infectious complication of COVID-19. MIS-C has overlapping features with other pediatric inflammatory disorders including Kawasaki Disease (KD), Macrophage Activation Syndrome (MAS), Toxic Shock Syndrome and sepsis. The exact mechanisms responsible for the clinical overlap between MIS-C and these conditions remain unclear, and biomarkers that could distinguish MIS-C from its clinical mimics are lacking. This study aimed to provide an overview of how proteomic methods, like Mass Spectrometry (MS) and affinity-based proteomics, can offer a detailed understanding of pathophysiology and aid in the diagnosis and prognosis of MIS-C.

METHODS

A narrative review of relevant studies published up to July 2024 was conducted.

RESULTS

We identified 15 studies and summarized their key proteomic findings. These studies investigated the serum or plasma proteome of MIS-C patients using MS, Proximity Extension, or Aptamer-based assays. The studies associated the proteomic profile of MIS-C with laboratory and clinical parameters and/or compared it with that of other diseases including acute COVID-19, KD, MAS, pediatric rheumatic diseases, sepsis and myocarditis or pericarditis following COVID-19 mRNA immunization. Depending on the method and the control group, different proteins were increased or decreased in the MIS-C group. The limitations and challenges in MIS-C proteomic research are also discussed, and future research recommendations are provided.

CONCLUSIONS

Although proteomics appear to be a promising approach for understanding the pathogenesis and uncovering candidate biomarkers in MIS-C, proteomic studies are still needed to recognize and validate biomarkers that could accurately discriminate MIS-C from its clinical mimics.

An Interim Report of a Phase 3, Long-Term, Open-Label Study to Evaluate Efficacy and Safety of Difamilast Ointment in Japanese Infants with Atopic Dermatitis

INTRODUCTION

Difamilast is the first selective phosphodiesterase 4 inhibitor approved for atopic dermatitis (AD) in Japan. A phase 3, 52-week, open-label study is ongoing to establish efficacy and safety of difamilast ointments in infants with AD aged 3 to < 24 months because a clinical study has not been conducted in this population.

METHODS

This study consisted of a 4-week primary evaluation period in which difamilast 0.3% ointment was applied twice daily to Japanese infants aged 3 to < 24 months (n = 41) and an ongoing 48-week long-term extension period in which difamilast 0.3% or 1% ointment was applied based on existing symptoms. The data on efficacy and safety of difamilast were obtained as of an interim report in the study period.

RESULTS

The response rate in Investigator's Global Assessment score was 45.0% at week 1, which was maintained at 56.1% at week 4 and 63.4% at the interim report. Infants achieved the response rate in Eczema Area and Severity Index 75 (improvement of ≥ 75%) of 47.5% at week 1, which further improved to 82.9% at week 4 and 78.1% at the interim report. Adverse events (AEs) were reported in 22 (53.7%) infants in the primary evaluation period: of those the most frequent AE was nasopharyngitis (19.5%) followed by dermatitis contact (7.3%). As of the interim report, 36 (87.8%) infants experienced AEs: of those, nasopharyngitis (70.7%) and gastroenteritis (22.0%) were most frequently observed. The total AEs were mostly mild or moderate in severity. No investigational medicinal product-related AEs and no AEs leading to discontinuation were reported.

CONCLUSION

Difamilast ointments applied twice daily to Japanese infants with AD aged 3 to < 24 months is effective and well tolerated as of the interim report in the study period. The final results will be reported in the near future.

CLINICAL TRIAL REGISTRATION

Clinical Trials. gov identifier: NCT05372653.

The Spectrum of Postacute Sequelae of COVID-19 in Children: From MIS-C to Long COVID

The effects of SARS-CoV-2 infection on children continue to evolve following the onset of the COVID-19 pandemic. Although life-threatening multisystem inflammatory syndrome in children (MIS-C) has become rare, long-standing symptoms stemming from persistent immune activation beyond the resolution of acute SARS-CoV-2 infection contribute to major health sequelae and continue to pose an economic burden. Shared pathophysiologic mechanisms place MIS-C and long COVID within a vast spectrum of postinfectious conditions characterized by intestinal dysbiosis, increased gut permeability, and varying degrees of immune dysregulation. Insights obtained from MIS-C will help shape our understanding of the more indolent and prevalent postacute sequelae of COVID and ultimately guide efforts to improve diagnosis and management of postinfectious complications of SARS-CoV-2 infection in children.

Proteomic mapping identifies serum marker signatures associated with MIS-C specific hyperinflammation and cardiovascular manifestation

Multisystem inflammatory syndrome in children (MIS-C) shares several clinical and immunological features with Kawasaki Disease (KD) and pediatric hyperinflammation, but the immuno-phenotypic overlap among these clinical mimics is still incompletely understood. Here we analyzed serum samples from treatment-naïve patients with MIS-C (n = 31) and KD (n = 11), pediatric hyperinflammation (n = 13) and healthy controls (HC, n = 10) by proximity extension assay (PEA) to profile 184 blood biomarkers. Collectively, immunophenotypic overlap between MIS-C and hyperinflammation exceeds overlap with KD. Overexpression of IL-17A in MIS-C and KD could best separate these conditions from hyperinflammatory conditions, while those were hallmarked by overabundance of adenosin deaminase and IL-18. Depletion in serum TNF-related subfamily member 9 (TNFRSF9) and apoptosis inducing ligand (TRAIL) linked with cardiovascular manifestations and myocarditis in MIS-C. Altogether, our analysis highlights important differences in molecular marker signatures also across different MIS-C and KD cohorts and suggests several previously unidentified molecular associations in context of cardiovascular inflammation.

Clinical and Laboratory Characteristics of Kawasaki Disease and COVID-19-Related Multisystem Inflammatory Syndrome in Children

Geographical and racial factors constitute important distinctions between Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C), but no study has been conducted in Vietnam. Forty-one children with KD from January 2018 to July 2020 and 42 with KD/MIS-C from August 2020 to December 2022 were included in this study. Of the patients, 52.3% were aged between 12 and 35 months. Only two were aged over 5 years, and both were belong to the KD/MIS-C group. A 59.5% of the patients were male. Apart from fever, all symptoms tended to be more frequent in patients with KD/MIS-C. The prevalence of diffuse skin rash, hand and foot edema or erythema and gastrointestinal signs was significantly higher in patients hospitalized with KD/MIS-C. There was no significant difference in laboratory findings between the two groups. Coronary artery dilation was more frequently observed in patients with KD/MIS-C compared to those with KD (40.5% vs. 14.6%, P = 0.009).

Unusual Manifestations of Kawasaki Disease in the COVID Era: A Case Series and Review of the Literature

Kawasaki disease (KD) is an acute medium-vessel vasculitis, mainly affecting infants older than six months and children under five years. It predisposes to the development of coronary artery aneurysms and constitutes the leading cause of acquired heart disease in children. Its diagnosis is based on clinical criteria, namely, fever lasting for ≥ five days together with at least four of the five principal clinical features of the disease. Occasionally, children with KD present with fever, but they fulfill only some of the five principal criteria, and this is described as incomplete KD. Furthermore, "atypical" KD is a term that is usually used for cases that appear with rather unusual clinical manifestations, which complicate clinical judgment and may delay diagnosis and treatment. In this case series, we present four cases of KD with rather unusual clinical features: a five-year-old boy with lobar pneumonia, a six-year-old girl with orange-brown chromonychia appearing on the 10th day of the disease, a 2.5-month-old infant with prolonged fever and urinary tract infection, and an 18-month-old infant with refractory KD and high suspicion of multisystem inflammatory syndrome in children (MIS-C). A literature review on the unusual manifestations of atypical KD was performed to identify clinical findings that must alert the clinician to consider this clinical entity.

Integration of scRNA-Seq and bulk RNA-Seq uncover perturbed immune cell types and pathways of Kawasaki disease

Introduction

Kawasaki disease (KD) is an acute febrile illness primarily affecting children and characterized by systemic inflammation and vasculitis that can lead to coronary artery complications. The aim of this study was to gain a comprehensive understanding of immune dysregulation in KD.

Methods

To this end, we employed integration of single-cell RNA sequencing (scRNA-Seq) and bulk RNA sequencing (bulk RNA-Seq) data. Furthermore, we conducted flow cytometry analysis for a cohort of 82 KD patients.

Results

Our analysis revealed significant heterogeneity within immune cell populations in KD patients, with distinct clusters of T cells, B cells, and natural killer (NK) cells. Importantly, CD4+ naïve T cells in KD patients were found to predominantly differentiate into Treg cells and Th2 cells, potentially playing a role in the excessive inflammation and vascular damage characteristic of the disease. Dysregulated signaling pathways were also identified, including the mTOR signaling pathway, cardiomyopathy pathway, COVID-19 signaling pathway, and pathways involved in bacterial or viral infection.

Discussion

These findings provide insights into the immunopathogenesis of KD, emphasizing the importance of immune cell dysregulation and dysregulated signaling pathways. Integration of scRNA-Seq and bulk RNA-Seq data offers a comprehensive view of the molecular and cellular alterations in KD and highlights potential therapeutic targets for further investigation. Validation and functional studies are warranted to elucidate the roles of the identified immune cell types and pathways in KD pathogenesis and to develop targeted interventions to improve patient outcomes.