Children account for only 1% to 2% of hospitalized patients with coronavirus disease 2019 (COVID-19).¹ However, in April 2020, severe systemic hyperinflammatory disease was reported in children in Europe and the United States, occurring 2 to 4 weeks after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.^2-6 This novel entity, named multisystem inflammatory syndrome in children (MIS-C)⁷ or pediatric multisystem inflammatory syndrome temporally associated with COVID-19,⁸ is associated with a wide range of clinical features including persistent fever, digestive symptoms, rash, bilateral nonpurulent conjunctivitis, mucocutaneous inflammation signs, and frequent cardiovascular involvement.^2,4-6,9 MIS-C is often associated with hemodynamic failure, with acute cardiac dysfunction requiring hemodynamic support in 60% to 75% of cases,^5,6 sometimes associated with death.^2-6

A recent increase in children admitted with hypotensive shock and fever in the context of the COVID-19 outbreak requires an urgent characterization and assessment of the involvement of SARS-CoV-2 infection. This is a case series performed at 4 academic tertiary care centers in Paris of all the children admitted to the pediatric intensive care unit (PICU) with shock, fever and suspected SARS-CoV-2 infection between April 15th and April 27th, 2020. 20 critically ill children admitted for shock had an acute myocarditis (left ventricular ejection fraction, 35% (25–55); troponin, 269 ng/mL (31–4607)), and arterial hypotension with mainly vasoplegic clinical presentation. The first symptoms before PICU admission were intense abdominal pain and fever for 6 days (1–10). All children had highly elevated C-reactive protein (> 94 mg/L) and procalcitonin (> 1.6 ng/mL) without microbial cause. At least one feature of Kawasaki disease was found in all children (fever, n = 20, skin rash, n = 10; conjunctivitis, n = 6; cheilitis, n = 5; adenitis, n = 2), but none had the typical form. SARS-CoV-2 PCR and serology were positive for 10 and 15 children, respectively. One child had both negative SARS-CoV-2 PCR and serology, but had a typical SARS-CoV-2 chest tomography scan. All children but one needed an inotropic/vasoactive drug support (epinephrine, n = 12; milrinone, n = 10; dobutamine, n = 6, norepinephrine, n = 4) and 8 were intubated. All children received intravenous immunoglobulin (2 g per kilogram) with adjuvant corticosteroids (n = 2), IL 1 receptor antagonist (n = 1) or a monoclonal antibody against IL-6 receptor (n = 1). All children survived and were afebrile with a full left ventricular function recovery at PICU discharge. Acute myocarditis with intense systemic inflammation and atypical Kawasaki disease is an emerging severe pediatric disease following SARS-CoV-2 infection. Early recognition of this disease is needed and referral to an expert center is recommended. A delayed and inappropriate host immunological response is suspected. While underlying mechanisms remain unclear, further investigations are required to target an optimal treatment.

COVID-19 mRNA vaccine immunogenicity and effectiveness are well established in adolescents.¹ However, the effect of vaccination on multisystem inflammatory syndrome in children (MIS-C),² a severe complication associated with SARS-CoV-2,³ has not yet been described. Summer 2021 in France was marked by both a fourth wave of COVID-19 cases due to the Delta variant, with a peak in August 2021, and by the recommendation of the French Public Health Agency to vaccinate children aged 12 years or older. We estimated the risk of MIS-C among adolescents by COVID-19 vaccination status during September 2021 and October 2021.

BACKGROUND: Initial reports on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in children suggested that very young age and comorbidities may increase risk of severe evolution, but these findings remained to be confirmed. We aimed to analyze the clinical spectrum of hospitalized pediatric SARS-CoV-2 infection and predictors of severe disease evolution. METHODS: We conducted a French national prospective surveillance of children hospitalized with SARS-CoV-2 infection. We included all children with confirmed SARS-CoV-2 infection in 60 hospitals during February 15 to June 1, 2020. The main outcome was the proportion of children with severe disease, defined by hemodynamic or ventilatory (invasive or not) support requirement. RESULTS: We included 397 hospitalized children with SARS-CoV-2 infection. We identified several clinical patterns, ranging from paucisymptomatic children, admitted for surveillance, to lower respiratory tract infection or multisystem inflammatory syndrome in children. Children <90 days old accounted for 37% of cases (145 of 397), but only 4 (3%) had severe disease. Excluding children with multisystem inflammatory syndrome in children (n = 29) and hospitalized for a diagnosis not related to SARS-CoV-2 (n = 62), 23 of 306 (11%) children had severe disease, including 6 deaths. Factors independently associated with severity were age ≥10 years (odds ratio [OR] = 3.4, 95% confidence interval: 1.1–10.3), hypoxemia (OR = 8.9 [2.6–29.7]), C-reactive protein level ≥80 mg/L (OR = 6.6 [1.4–27.5]). CONCLUSIONS: In contrast with preliminary reports, young age was not an independent factor associated with severe SARS-CoV-2 infection, and children <90 days old were at the lowest risk of severe disease evolution. This may help physicians to better identify risk of severe disease progression in children.

Hyperimmunoglobulinemia D is the less severe form of mevalonate kinase deficiency (MKD) caused by recessive inherited mutation in the mevalonate kinase gene. Hyperimmunoglobulinemia D is characterized by febrile attacks, often associated with transient digestive manifestations, such as abdominal pain, diarrhea, and vomiting. Here we report for the first time 2 patients with MKD revealed by severe neonatal colitis. Both patients had chronic bloody diarrhea and failure to thrive; 1 patient since the age of 1 month and the other since the age of 12 days. Total parenteral nutrition was required. A marked elevation of acute phase reactants was present, and no evidence of infection was found. In patient 1, ileocolonoscopy revealed ulcerative colitis at the age of 5 months. Patient 2 suffered from enterocolitis and shock, associated with multiple bowel adhesions at age 5 weeks; the rectosigmoidoscopy showed aphtoid lesions of the sigmoid colon. Pathologic findings of colonic biopsies revealed a dense polymorph inflammatory infiltrate associated with deep ulcerations. Febrile attacks occurred 2 months after the onset of digestive symptoms in patient 1, and at onset of disease in patient 2. Genomic sequencing of the mevalonate kinase gene revealed compound heterozygous mutations in both patients. Anti-interleukin-1 agent produced long-term remission of all digestive features and laboratory parameters. This report emphasizes that MKD may be the cause of severe early-onset inflammatory colitis, and must be considered by physicians, even in the absence of fever, after ruling out infections. Anti-interleukin-1 therapy may result in a dramatic improvement of MKD-related inflammatory bowel disease.