Two studies today describe new findings in the COVID-19-associated multisystem inflammatory syndrome in children (MIS-C) and the distinct but similar Kawasaki disease (KD).
Low blood pressure, shock, heart dysfunction
In the first study, published in JAMA Pediatrics, a team led by researchers from the US Centers for Disease Control and Prevention (CDC) used laboratory data to compare the geographical and temporal distribution of MIS-C from March 2020 to January 2021 with COVID-19 in the same period.
In the largest known cohort of MIS-C patients and their distributions across the United States, the cumulative incidence was 2.1
Of the 1,733 MIS-C patients, 90.4% had involvement in at least four organ systems, 54% had low blood pressure or shock, 58.2% required intensive care, and 31.0% had abnormal heart function. Pericardial effusion (fluid buildup in the sac around the heart) occurred in 23.4%, myocarditis (inflammation of the heart muscle) in 17.3% and coronary artery dilatation or aneurysm (ballooning of a vessel wall) in 16.5%.
Patients aged 18 to 20 years had the most severe MIS-C signs and symptoms, with 30.9% having myocarditis, 36.4% having pneumonia and 18.2% having acute respiratory distress syndrome (ARDS). This age group also most likely reported having a previous coronavirus-like disease (63%). In contrast, children 0 to 4 years of age had the fewest severe MIS-C signs and symptoms, but 38.4% had low blood pressure or shock, and 44.3% required intensive care.
Gastrointestinal symptoms, rash and conjunctival hyperemia (an inflammatory eye disorder) occurred in 53% to 67% of MIS-C patients. Other common symptoms included fever, vomiting, rash and diarrhea. Among all MIS-C patients, 57.6% were boys, 71.3% were Hispanic or black, and the median age was 9 years.
Delayed immune response to coronavirus
States with the heaviest burden of MIS-C were generally in the West and Midwest. The first two nationwide peaks of MIS-C occurred 2 to 5 weeks after COVID-19 spikes and virus spread from urban to rural areas.
Most cases of MIS-C are thought to occur after asymptomatic or mild COVID-19 infections with an excessive inflammatory response that coincides with maximal antibody production several weeks later, the authors said.
“The geographical and temporal association between MIS-C and the COVID-19 pandemic suggested that MIS-C was due to delayed immunological responses to SARS-CoV-2 infection,” they wrote. “The clinical manifestations varied by age and by the presence or absence of previous COVID-19.”
The researchers called for the development of laboratory markers or diagnostic tests to distinguish between MIS-C and severe COVID-19 and other inflammatory conditions such as Kawasaki disease. “Physicians should maintain a high level of suspicion that MIS-C can immediately diagnose and treat these patients,” they concluded.
In a commentary in the same journal, Jennifer Blumenthal, MD, and Jeffrey Burns, MD, MPH, both from Boston Children’s Hospital, said the study results show that the lack of previous coronavirus symptoms, especially in younger children, should not reassure pediatricians that MIS C has not affected their hearts.
“If the worldwide pediatric population is at risk of COVID-19 and vaccination will be delayed in the pediatric population compared to adults, this potentially serious outcome should remain at the forefront of the differential diagnosis for pediatricians worldwide pending further research results. , “they wrote.
Kawasaki’s disease probably spread in the air
Published in JAMA Network Open, the second study was led by researchers at Fukuoka Children’s Hospital in Japan to determine the role of droplet versus contact transmission of KD. The longitudinal study included 1,649 patients with KD and 15,586 patients with infectious diseases admitted to six centers from 2015 to 2020.
KD is an acute disease that mainly affects children 6 months to 5 years – the median age in the KD cohort was 25 months – and has inflammation of small and medium-sized blood vessels. Although the cause of KD is unknown, it is thought to occur in genetically predisposed children after exposure to an environmental trigger such as an infection.
The researchers found that the number of hospital admissions for KD did not change significantly between April and May in 2015 to 2019 compared to the same months in 2020 (averaging 24.8 versus 18.0 admissions per month; 27.4% decrease; adjusted incidence rate [aIRR](0.73).
During the same period, however, hospital admissions for droplet or contact-transmitted respiratory infections fell from an average of 157.6 to 39.0 admissions per day. Month, a decrease of 75.3% (aIRR, 0.25), as well as those for gastrointestinal infections (43.8 to 6.0 monthly admissions), a decrease of 86.3% (aIRR, 0.14) for 12.254 fewer infections.
As a result, the ratio of KD to droplet or contact-transmitted respiratory infections and gastrointestinal infections increased significantly in April and May 2020 (ratio, 0.40 vs 0.12).
“These findings suggest that contact or droplet transmission is not an important route for KD development in Japan and support the results of previous epidemiological studies indicating that KD may in most cases be associated with airborne disease. More comprehensive studies are entitled to further understanding of this exciting disease, “the authors wrote.