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In another sign that the COVID-19-associated multisystem inflammatory syndrome in children (MIS-C) is not your typical Kawasaki disease, a center in Paris reported that fully 57% of its cases were in children of African ancestry.

Only 14% of the 21 patients had a parent born in Asia, whereas the high-risk population for Kawasaki disease is typically of Asian descent, reported Martin Chalumeau, MD, of Necker-Enfants Malades University Hospital in Paris, and colleagues in .

"These clinical findings should prompt high vigilance among primary care and emergency doctors, and preparedness during the coronavirus disease 2019 pandemic in countries with a high proportion of children of African ancestry and high levels of community transmission," they wrote.

While French law , 14% to 17% of the metropolitan population is to be black.

The findings follow a series in The Lancet in May in which of "hyperinflammatory shock" found over a 10-day period during the COVID-19 pandemic in southeast England were children of Afro-Caribbean descent.

In the U.S., no findings have detailed race or ethnic background of MIS-C cases, but there has been a clear disproportionate burden of COVID-19 among non-Hispanic black populations, which has been suggested to be due to socioeconomic and healthcare disparities, as well as higher prevalence of chronic diseases.

In the French cohort, the MIS-C patients "had no relevant personal or family medical history, and none reported living in unhealthy environments or social housing," the researchers noted.

Genetic and immunological mechanisms are other possible explanations, they added.

The study of 21 patients, ages 18 years and younger, who were admitted to a single referral center in Paris over a 15-day period from April 27 through May 11, 2020, and who had features of Kawasaki disease, highlighted a number of other contrasts with classic Kawasaki disease:

• Median age 7.9 years (range 3.7-16.6) vs 6 months to 5 years
• GI symptoms in 100% vs uncommon
• Kawasaki disease shock syndrome 57% vs 2% to 7%
• Myocarditis with ventricular dysfunction in 76% vs <1%
• ICU support 81% vs 4%
• Lymphopenia in 81% vs rare
• Coronary artery dilation or aneurysm in 24% vs 4% to 13%

None of the 21 MIS-C patients had left home for school, social gatherings, or travel since the lockdown started March 17, according to their parents. Nine had viral-like symptoms a median 45 (range 18-79) days prior to Kawasaki-like symptom onset. Ten had contact with family members displaying viral-like symptoms (five highly suspicious of COVID-19) a median 36 days prior.

Those findings match reports starting in late April from around Europe and the U.S. indicating that MIS-C popped up suddenly, trailing about a month behind the surge of COVID-19 cases. Although the two have not been causally linked, the mechanism is speculated to be similar to that suspected for Kawasaki disease.

"Such a delay between the peak of SARS-CoV-2 infections and presentation of PIMS [pediatric multisystem inflammatory syndrome temporally associated with COVID-19] raises the possibility that this is a post-infectious, immunologically mediated phenomenon of covid-19," noted Mary Beth Son, MD, of Boston Children's Hospital, in an .

Only one of the children in the Parisian cohort had active symptoms of COVID-19 (anosmia), 38% had a positive RT-PCR test for SARS-CoV-2, and 90% had positive immunoglobulin G antibodies.

All the children recovered with a median 8 days in the hospital during which all got high-dose IV immunoglobulin (with a second dose for 24% who showed resistance) and low-dose aspirin. Seven got concomitant corticosteroids; 86% got empiric broad-spectrum antibiotic treatment.

"It seems highly likely that more reports will appear from around the globe as recent peaks of SARS-CoV-2 infections in new regions result in waves of PIMS in children and adolescents," Son wrote. "Urgent issues that will be best tackled by an international, multidisciplinary pediatric community include determination of the incidence and spectrum of mild to severe PIMS through systematic surveillance; best treatment strategies; the incidence and clinical course of coronary artery dilation, aneurysms, and other cardiac complications and their association with risk factors such as severity of presenting illness; and non-cardiac long term health sequelae."

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