Temporal Clusters of Kawasaki Disease Cases Share Distinct Phenotypes That Suggest Response to Diverse Triggers

Multisystem inflammatory syndrome in children associated with COVID-19: from pathophysiology to clinical management and outcomes

Multisystem inflammatory syndrome in children (MIS-C), also known as pediatric inflammatory multisystem syndrome (PIMS), is a new postinfectious illness associated with COVID-19, affecting children after SARS-CoV-2 exposure. The hallmarks of this disorder are hyperinflammation and multisystem involvement, with gastrointestinal, cardiac, mucocutaneous, and hematologic disturbances seen most commonly. Cardiovascular involvement includes cardiogenic shock, ventricular dysfunction, coronary artery abnormalities, and myocarditis. Now entering the fourth year of the pandemic, clinicians have gained some familiarity with the clinical presentation, initial diagnosis, cardiac evaluation, and treatment of MIS-C. This has led to an updated definition from the Centers for Disease Control and Prevention in the USA driven by increased experience and clinical expertise. Furthermore, the available evidence established expert consensus treatment recommendations supporting a combination of immunoglobulin and steroids. However, the pathophysiology of the disorder and answers to what causes this remain under investigation. Fortunately, long-term outcomes continue to look promising, although continued follow-up is still needed. Recently, COVID-19 mRNA vaccination is reported to be associated with reduced risk of MIS-C, while further studies are warranted to understand the impact of COVID-19 vaccines on MIS-C. We review the findings and current literature on MIS-C, including pathophysiology, clinical features, evaluation, management, and medium- to long-term follow-up outcomes.

Classification and epidemiology of vasculitis: Emerging concepts

The recent publication of the American College of Rheumatology (ACR)-European Alliance of Associations for Rheumatology (EULAR) classification criteria for large vessel vasculitis and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAVs) has provided modern criteria for the classification of these conditions, which incorporate contemporary methods of investigation and diagnosis. Further validation is required in independent cohorts, especially from populations that were not well represented in the development cohort. Studies of the occurrence of large vessel vasculitis report that Takayasu arteritis is a rare disease in most populations, and giant cell arteritis is the most common vasculitis in older populations. The incidence of AAV appears to have plateaued, but the prevalence is increasing as a result of lower mortality. The new classification criteria may affect the reported incidence and prevalence, and studies will be needed to confirm this. The impact of COVID-19 on the occurrence of the vasculitides is not completely known, but there is evidence of reduced occurrence of Kawasaki disease and IgA-associated vasculitis following lockdowns with reduced transmission of possible trigger infectious agents.

COVID-19 Positive Versus Negative Complete Kawasaki Disease: A Study from the International Kawasaki Disease Registry

To determine clinical differences for children with complete Kawasaki disease (KD) with and without evidence of preceding SARS-CoV-2 infection. From January 2020, contemporaneous patients with complete KD criteria were classified as either SARS-CoV-2 positive (KDCOVID+; confirmed household exposure, positive PCR and/or serology) or SARS-CoV-2 negative (KDCOVID-; negative testing and no exposure) and compared. Of 744 patients in the International Kawasaki Disease Registry, 52 were KDCOVID- and 61 were KDCOVID+. KDCOVID+ patients were older (median 5.5 vs. 3.7 years; p < 0.001), and all additionally met diagnostic criteria for multisystem inflammatory syndrome in children (MIS-C). They were more likely to have abdominal pain (60% vs. 35%; p = 0.008) and headache (38% vs. 10%; p < 0.001) and had significantly higher CRP, troponin, and BUN/creatinine, and lower hemoglobin, platelets, and lymphocytes. KDCOVID+ patients were more likely to have shock (41% vs. 6%; p < 0.001), ICU admission (62% vs. 10%; p < 0.001), lower left ventricular ejection fraction (mean lowest LVEF 53% vs. 60%; p < 0.001), and to have received inotropic support (60% vs. 10%; p < 0.001). Both groups received IVIG (2 doses in 22% vs. 18%; p = 0.63), but KDCOVID+ were more likely to have received steroids (85% vs. 35%; p < 0.001) and anakinra (60% vs. 10%; p = 0.002). KDCOVID- patients were more likely to have medium/large coronary artery aneurysms (CAA, 12% vs. 0%; p = 0.01). KDCOVID+ patients differ from KDCOVID-, have more severe disease, and greater evidence of myocardial involvement and cardiovascular dysfunction rather than CAA. These patients may be a distinct KD phenotype in the presence of a prevalent specific trigger.

Epidemiological and Clinical Features of Kawasaki Disease During the COVID-19 Pandemic in the United States

IMPORTANCE

Public health measures implemented during the COVID-19 pandemic had widespread effects on population behaviors, transmission of infectious diseases, and exposures to environmental pollutants. This provided an opportunity to study how these factors potentially influenced the incidence of Kawasaki disease (KD), a self-limited pediatric vasculitis of unknown etiology.

OBJECTIVES

To examine the change in KD incidence across the United States and evaluate whether public health measures affected the prevalence of KD.

DESIGN, SETTING, AND PARTICIPANTS

This multicenter cohort study included consecutive, unselected patients with KD who were diagnosed between January 1, 2018, and December 31, 2020 (multicenter cohort with 28 pediatric centers), and a detailed analysis of patients with KD who were diagnosed between January 1, 2002, and November 15, 2021 (Rady Children's Hospital San Diego [RCHSD]).

MAIN OUTCOMES AND MEASURES

For the multicenter cohort, the date of fever onset for each patient with KD was collected. For RCHSD, detailed demographic and clinical data as well as publicly available, anonymized mobile phone data and median household income by census block group were collected. The study hypothesis was that public health measures undertaken during the pandemic would reduce exposure to the airborne trigger(s) of KD and that communities with high shelter-in-place compliance would experience the greatest decrease in KD incidence.

RESULTS

A total of 2461 KD cases were included in the multicenter study (2018: 894; 2019: 905; 2020: 646), and 1461 cases (median [IQR] age, 2.8 years [1.4-4.9 years]; 900 [61.6%] males; 220 [15.1%] Asian, 512 [35.0%] Hispanic, and 338 [23.1%] White children) from RCHSD between 2002 and 2021 were also included. The 28.2% decline in KD cases nationally during 2020 (646 cases) compared with 2018 (894 cases) and 2019 (905 cases) was uneven across the United States. For RCHSD, there was a disproportionate decline in KD cases in 2020 to 2021 compared with the mean (SD) number of cases in earlier years for children aged 1 to 5 years (22 vs 44.9 [9.9]; P = .02), male children (21 vs 47.6 [10.0]; P = .01), and Asian children (4 vs 11.8 [4.4]; P = .046). Mobility data did not suggest that shelter-in-place measures were associated with the number of KD cases. Clinical features including strawberry tongue, enlarged cervical lymph node, and subacute periungual desquamation were decreased during 2020 compared with the baseline period (strawberry tongue: 39% vs 63%; P = .04; enlarged lymph node: 21% vs 32%; P = .09; periungual desquamation: 47% vs 58%; P = .16). School closures, masking mandates, decreased ambient pollution, and decreased circulation of respiratory viruses all overlapped to different extents with the period of decreased KD cases. KD in San Diego rebounded in the spring of 2021, coincident with lifting of mask mandates.

CONCLUSIONS AND RELEVANCE

In this study of epidemiological and clinical features of KD during the COVID-19 pandemic in the United States, KD cases fell and remained low during the period of masking and school closure. Mobility data indicated that differential intensity of sheltering in place was not associated with KD incidence. These findings suggest that social behavior is associated with exposure to the agent(s) that trigger KD and are consistent with a respiratory portal of entry for the agent(s).

An Artificial Intelligence-guided signature reveals the shared host immune response in MIS-C and Kawasaki disease

Multisystem inflammatory syndrome in children (MIS-C) is an illness that emerged amidst the COVID-19 pandemic but shares many clinical features with the pre-pandemic syndrome of Kawasaki disease (KD). Here we compare the two syndromes using a computational toolbox of two gene signatures that were developed in the context of SARS-CoV-2 infection, i.e., the viral pandemic (ViP) and severe-ViP signatures and a 13-transcript signature previously demonstrated to be diagnostic for KD, and validated our findings in whole blood RNA sequences, serum cytokines, and formalin fixed heart tissues. Results show that KD and MIS-C are on the same continuum of the host immune response as COVID-19. Both the pediatric syndromes converge upon an IL15/IL15RA-centric cytokine storm, suggestive of shared proximal pathways of immunopathogenesis; however, they diverge in other laboratory parameters and cardiac phenotypes. The ViP signatures reveal unique targetable cytokine pathways in MIS-C, place MIS-C farther along in the spectrum in severity compared to KD and pinpoint key clinical (reduced cardiac function) and laboratory (thrombocytopenia and eosinopenia) parameters that can be useful to monitor severity.

Global epidemiology of vasculitis

The many forms of vasculitis are characterized by inflammation of blood vessels, leading to potentially long-term sequelae including vision loss, aneurysm formation and kidney failure. Accurate estimation of the incidence and prevalence has been hampered by the absence of reliable diagnostic criteria and the rarity of these conditions; however, much progress has been made over the past two decades, although data are still lacking from many parts of the world including the Indian subcontinent, China, Africa and South America. Giant cell arteritis occurs in those aged 50 years and over and seems to mainly affect persons of northern European ancestry, whereas Takayasu arteritis occurs mainly in those aged under 40 years. By contrast, Kawasaki disease mainly occurs in children aged under 5 years and is most common in children of Asian ancestry, and IgA vasculitis occurs in children and adolescents. Although much less common than giant cell arteritis, the different forms of antineutrophil cytoplasmic antibody-associated vasculitis are being increasingly recognized in most populations and occur more frequently with increasing age. Behçet syndrome occurs most commonly along the ancient silk road between Europe and China. Much work needs to be done to better understand the influence of ethnicity, geographical location, environment and social factors on the development of vasculitis.

Temporal clustering of Kawasaki disease cases around the world

In a single-site study (San Diego, CA, USA), we previously showed that Kawasaki Disease (KD) cases cluster temporally in bursts of approximately 7 days. These clusters occurred more often than would be expected at random even after accounting for long-term trends and seasonality. This finding raised the question of whether other locations around the world experience similar temporal clusters of KD that might offer clues to disease etiology. Here we combine data from San Diego and nine additional sites around the world with hospitals that care for large numbers of KD patients, as well as two multi-hospital catchment regions. We found that across these sites, KD cases clustered at short time scales and there were anomalously long quiet periods with no cases. Both of these phenomena occurred more often than would be expected given local trends and seasonality. Additionally, we found unusually frequent temporal overlaps of KD clusters and quiet periods between pairs of sites. These findings suggest that regional and planetary range environmental influences create periods of higher or lower exposure to KD triggers that may offer clues to the etiology of KD.

An AI-guided signature reveals the nature of the shared proximal pathways of host immune response in MIS-C and Kawasaki disease

A significant surge in cases of multisystem inflammatory syndrome in children (MIS-C, also called Pediatric Inflammatory Multisystem Syndrome - PIMS) has been observed amidst the COVID-19 pandemic. MIS-C shares many clinical features with Kawasaki disease (KD), although clinical course and outcomes are divergent. We analyzed whole blood RNA sequences, serum cytokines, and formalin fixed heart tissues from these patients using a computational toolbox of two gene signatures, i.e., the 166-gene viral pandemic (ViP) signature, and its 20-gene severe (s)ViP subset that were developed in the context of SARS-CoV-2 infection and a 13-transcript signature previously demonstrated to be diagnostic for KD. Our analyses revealed that KD and MIS-C are on the same continuum of the host immune response as COVID-19. While both the pediatric syndromes converge upon an IL15/IL15RA -centric cytokine storm, suggestive of shared proximal pathways of immunopathogenesis, they diverge in other laboratory parameters and cardiac phenotypes. The ViP signatures also revealed unique targetable cytokine pathways in MIS-C, place MIS-C farther along in the spectrum in severity compared to KD and pinpoint key clinical (reduced cardiac function) and laboratory (thrombocytopenia and eosinopenia) parameters that can be useful to monitor severity.

Associations between the spatiotemporal distribution of Kawasaki disease and environmental factors: evidence supporting a multifactorial etiologic model

The etiology of Kawasaki Disease (KD), the most common cause of acquired heart disease in children in developed countries, remains elusive, but could be multifactorial in nature as suggested by the numerous environmental and infectious exposures that have previously been linked to its epidemiology. There is still a lack of a comprehensive model describing these complex associations. We present a Bayesian disease model that provides insight in the spatiotemporal distribution of KD in Canada from 2004 to 2017. The disease model including environmental factors had improved Watanabe-Akaike information criterion (WAIC) compared to the base model which included only spatiotemporal and demographic effects and had excellent performance in recapitulating the spatiotemporal distribution of KD in Canada (98% and 86% spatial and temporal correlations, respectively). The model suggests an association between the distribution of KD and population composition, weather-related factors, aeroallergen exposure, pollution, atmospheric concentration of spores and algae, and the incidence of healthcare encounters for bacterial pneumonia or viral intestinal infections. This model could be the basis of a hypothetical data-driven framework for the spatiotemporal distribution of KD. It also generates novel hypotheses about the etiology of KD, and provides a basis for the future development of a predictive and surveillance model.