Currently, two studies describe new findings in the multi-system inflammatory syndrome in children associated with COVID-19 (MIS-C) and different 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 U.S. Centers for Disease Control and Prevention (CDC) used laboratory data to compare the geographic and temporal distribution of MIS-C from March 2020 to January 2021 with the of COVID-19 during the same period.
In the largest known cohort of MIS-C patients and their distributions in the United States, the cumulative incidence was 2.1 per 100,000 people 21 years of age and younger and ranged by state, from 0.2 to 6.3 per 100,000. The mortality rate was 1.4%.
Of the 1,733 patients with MIS-C, 90.4% had involvement of at least four organ systems, 54% had low blood pressure or shock, 58.2% required intensive care, and 31.0% had a abnormal heart function. There was pericardial effusion (accumulation of fluid in the sac around the heart) in 23.4%, myocarditis (inflammation of the heart muscle) in 17.3%, and dilatation of the coronary artery or aneurysm (bulging of the wall of the vessel ) in 16.5%.
Patients aged 18 to 20 years had the most severe signs and symptoms of MIS-C, with 30.9% with myocarditis, 36.4% with pneumonia, and 18.2% with acute respiratory distress syndrome (ARDS) . This age group was also more likely to report having had a previous coronavirus-like illness (63%). In contrast, children 0 to 4 years old had the fewest serious signs and symptoms of MIS-C, but 38.4% had low blood pressure or shock, and 44.3% required intensive care.
Gastrointestinal symptoms, skin rash, and conjunctival hyperemia (an inflammatory eye condition) occurred in 53% to 67% of MIS-C patients. Other common symptoms included fever, vomiting, rash, and diarrhea. Among all patients with MIS-C, 57.6% were male, 71.3% were Hispanic or Black, and the median age was 9 years.
Delayed immune response to coronavirus
The states with the highest load of MIS-C were generally in the West and Midwest. The first two nationwide spikes in MIS-C occurred 2 to 5 weeks after the COVID-19 spikes and viral spread from urban to rural areas.
Most cases of MIS-C are believed to occur after asymptomatic or mild COVID-19 infections, with an inordinate inflammatory response coinciding with peak antibody production several weeks later, the authors said.
“The geographic and temporal association of MIS-C with the COVID-19 pandemic suggested that MIS-C resulted from delayed immune responses to SARS-CoV-2 infection,” they wrote. “The clinical manifestations varied according to age and the presence or absence of the previous COVID-19.”
The researchers called for the development of laboratory markers or diagnostic tests to distinguish MIS-C from severe COVID-19 and other inflammatory conditions such as Kawasaki disease. “Clinicians must maintain a high index of suspicion for MIS-C to rapidly diagnose and treat these patients,” they concluded.
In a comment in the same journal, Jennifer Blumenthal, MD, and Jeffrey Burns, MD, MPH, both of Boston Children’s Hospital, said study findings show that a lack of prior coronavirus symptoms, especially in younger children, does not it should reassure pediatricians that MIS-C has not affected their hearts.
“If the entire global pediatric population is at risk for COVID-19 and vaccination is to be delayed in the pediatric population compared to adults, this potentially serious outcome should remain at the forefront of differential diagnosis for pediatricians across the world. world awaiting further research results, “they wrote.
Kawasaki disease is likely to spread through the air
Published in Open JAMA network, the second study was led by researchers at the Fukuoka Children’s Hospital in Japan to determine the role of droplet transmission versus contact transmission of KD. The longitudinal study involved 1,649 KD patients and 15,586 infectious disease patients hospitalized at six centers from 2015 to 2020.
KD is an acute disease that mainly affects children aged 6 months to 5 years (the median age in the KD cohort was 25 months) and presents inflammation of the small and medium blood vessels. Although the cause of KD is unknown, it is believed to occur in children with a genetic predisposition after exposure to an environmental trigger, such as an infection.
The researchers found that the number of KD hospitalizations did not change significantly between April and May 2015 to 2019 compared to the same months in 2020 (mean, 24.8 vs. 18.0 admissions per month; decrease of 27.4% ; adjusted incidence rate index [aIRR], 0.73).
During the same time, however, hospitalizations for droplet- or contact-borne respiratory tract infections fell from a mean of 157.6 to 39.0 admissions per month, a decrease of 75.3% (aIRR, 0.25 ), as well as those of 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 proportion of KD to gastrointestinal and respiratory tract infections transmitted by droplets or by contact 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 the development of KD in Japan and support findings from previous epidemiological studies that KD may be associated with airborne diseases in most of Japan. cases. Larger studies are required for a better understanding of this intriguing disease, “the authors wrote.