MIS-C and Kawasaki disease phenotypes
Earlier in the pandemic, when MIS-C first emerged, it was compared with Kawasaki disease (KD). “However, a closer examination of the literature shows that only about one-quarter to half of patients with a reported diagnosis of MIS-C meet the full diagnostic criteria for KD,” the authors wrote. Key features that separate MIS-C from KD include the greater incidence of KD among children in Japan and East Asia versus the higher incidence of MIS-C among non-Hispanic Black children. In addition, children with MIS-C have shown a wider age range, more prominent gastrointestinal and neurologic symptoms, and more frequent cardiac dysfunction, compared with those with KD.
Close follow-up with cardiology is essential for children with MIS-C, according to the authors. The recommendations call for repeat echocardiograms for all children with MIS-C at a minimum of 7-14 days, then again at 4-6 weeks after the initial presentation. The authors also recommended additional echocardiograms for children with left ventricular dysfunction and cardiac aortic aneurysms.
Current treatment recommendations emphasize that patients under investigation for MIS-C with life-threatening manifestations may need immunomodulatory therapy before a full diagnostic evaluation is complete, the authors said. However, patients without life-threatening manifestations should be evaluated before starting immunomodulatory treatment to avoid potentially harmful therapies for pediatric patients who don’t need them.
When MIS-C is refractory to initial immunomodulatory treatment, a second dose of IVIg is not recommended, but intensification therapy is advised with either high-dose (10-30 mg/kg per day) glucocorticoids, anakinra, or infliximab. However, there is little evidence available for selecting a specific agent for intensification therapy.
The task force also advises giving low-dose aspirin (3-5 mg/kg per day, up to 81 mg once daily) to all MIS-C patients without active bleeding or significant bleeding risk until normalization of the platelet count and confirmed normal coronary arteries at least 4 weeks after diagnosis.
COVID-19 and hyperinflammation
The task force also noted a distinction between MIS-C and severe COVID-19 in children. Although many children with MIS-C are previously healthy, most children who develop severe COVID-19 during an initial infection have complex conditions or comorbidities such as developmental delay or genetic anomaly, or chronic conditions such as congenital heart disease, type 1 diabetes, or asthma, the authors said. They recommend that “hospitalized children with COVID-19 requiring supplemental oxygen or respiratory support should be considered for immunomodulatory therapy in addition to supportive care and antiviral medications.”
The authors acknowledged the limitations and evolving nature of the recommendations, which will continue to change and do not replace clinical judgment for the management of individual patients. In the meantime, the ACR will support the task force in reviewing new evidence and providing revised versions of the current document.
Many questions about MIS-C remain, Dr. Henderson said in an interview. “It can be very hard to diagnose children with MIS-C because many of the symptoms are similar to those seen in other febrile illness of childhood. We need to identify better biomarkers to help us make the diagnosis of MIS-C. In addition, we need studies to provide information about what treatments should be used if children fail to respond to IVIg and steroids. Finally, it appears that vaccination [against SARS-CoV-2] protects against severe forms of MIS-C, and studies are needed to see how vaccination protects children from MIS-C.”
The development of the guidance was supported by the American College of Rheumatology. Dr. Henderson disclosed relationships with companies including Sobi, Pfizer, and Adaptive Biotechnologies (less than $10,000) and research support from the Childhood Arthritis and Rheumatology Research Alliance and research grant support from Bristol-Myers Squibb.
A version of this article first appeared on.