Key Points Question What are the clinical characteristics of multisystem inflammatory syndrome in adults (MIS-A)? Findings This systematic review of patients with MIS-A reported in the literature and to the US Centers for Disease Control and Prevention identified 221 patients worldwide. The syndrome presented approximately 4 weeks after acute COVID-19 with hyperinflammation and extrapulmonary multiorgan involvement that may be difficult to discern from acute biphasic COVID-19 and postacute sequelae of SARS-CoV-2 infection. Meaning These findings suggest that MIS-A occurs in the postacute COVID-19 period with a heterogeneous clinical presentation likely owing to a dysregulated immune response.

Background Detection of coronary artery lesions (CALs) at initial echocardiography can aid in diagnosing Kawasaki disease (KD) and inform primary adjunctive treatments. We aimed to characterize patients with KD with CALs detected at initial echocardiography. Methods and Results We analyzed data from the nationwide Japanese KD survey that contained information on 103 222 population‐based patients diagnosed with KD across Japan during 2011 to 2018. Patients with CALs detected at initial echocardiography were assessed by age, day of illness, and number of principal KD signs (≥3). Multivariable logistic regression analysis was performed to evaluate factors independently associated with CAL detection. Overall, 3707 (3.6%) patients had CALs detected at initial echocardiography. Patients aged <12 and ≥60 months were associated with CAL detection (adjusted odds ratio [95% CI], 1.28 [1.18‒1.39] and 1.32 [1.20‒1.45], respectively; reference, 12‒59 months). Patients with delayed hospital visits were increasingly at higher risk for CAL detection (days 7‒8, 1.84 [1.63‒2.08]; days 9–10, 4.30 [3.58–5.15]; and days ≥11, 9.12 [7.63‒10.90]; reference, days 1–4). Patients with 3 or 4 principal KD signs were independently associated with CAL detection (1.75 [1.63‒1.88]). These patients were significantly more likely to be aged <12 months but were not associated with delayed hospital visit. Younger patients visited at earlier days of illness. Conclusions Timely diagnosis could be beneficial for patients with KD. However, even when the hospital visit occurred early in the course of illness, patients with 3 or 4 principal KD signs, especially younger patients, were at higher risk of CAL detection at initial echocardiography.

Background: Kawasaki disease (KD) can result in severe coronary artery abnormalities (CAAs). Corticosteroids added to initial standard intravenous immunoglobulin (IVIG) treatment may decrease the risk for these complications. Different corticosteroid regimens (single-day high dose pulse vs multiple lower doses) may contribute to the discrepant results of prior studies. Methods: Using data from the 22nd, 23 rd , and 24th Japanese nationwide KD surveys (2011-2016), we identified KD patients who did not have CAAs at first presentation and who were treated with either pulse or multiple-dose corticosteroids as part of their initial treatment. Occurrence of subsequent CAAs and treatment failure were compared between the treatment regimens and adjusted odds ratios were calculated controlling for sex, age group, illness day at first treatment, survey, and recurrent KD. Results: There were 782 KD patients who received pulse corticosteroid treatment and 4,817 who received multiple dose treatment. Patients receiving multiple dose treatment were less likely to develop CAAs (5.5% vs 8.3%, OR 0.64; 95% CI: 0.48-0.85) or treatment failure (21.4% vs 41.6%; OR: 0.38; 95% CI: 0.33-0.45). Adjusted analyses showed similar protective effects of multiple-dose treatment against CAAs (OR: 0.67, 95% CI: 0.51-0.90) and treatment failure (OR: 0.39, 95% CI: 0.33-0.46). Conclusions: Multiple-dose corticosteroid combination treatment resulted in substantially improved outcomes in KD patients compared to pulse treatment. For patients who may be at elevated risk of treatment failure or CAA, use of multiple-dose corticosteroids in conjunction with IVIG is likely to provide considerable clinical benefit.

Background Classification of MIS-C, COVID-19, and other pediatric inflammatory conditions is challenged by phenotypic overlap and absence of diagnostic laboratory evidence. Due to public health need and based on limited data from early cases, CDC developed a necessarily broad MIS-C surveillance case definition in May 2020. Studies have since shown that some criteria do not distinguish between MIS-C and other conditions and may contribute to misclassification. To inform planned revision to the CDC definition, we evaluated the impact of narrowing these criteria on case inclusion in national MIS-C surveillance. Methods Of state and local health-department reported cases meeting the current MIS-C case definition as of 04/14/2022, we describe the proportion that met revised criteria under consideration including fever duration, C-reactive protein (CRP) elevation using a defined cutoff, and organ involvement represented by specific criteria. We also evaluated cases identified using potential combinations of revised criteria. Results Of 8,096 MIS-C cases fulfilling the original case definition, 6,332 (78%) had sufficient data for evaluation of criteria. Of these, 96% had fever for ≥2 days and 94% had a CRP ≥ 3.0 mg/dL (Table 1). Cardiac involvement defined by key features of MIS-C was present in 84% of cases (62% if BNP/proBNP elevation was excluded); 43% had shock. Dermatologic, gastrointestinal (GI) and hematologic involvement were present in 75%, 89% and 37% of cases, respectively. Neurologic (excluding headache), renal, and respiratory involvement were present in 16%, 20%, and 63% of cases, respectively. The number of cases with ≥ 2 of cardiac (without BNP/proBNP elevation), shock, dermatologic, GI, or hematologic involvement was 5,733 (91%). SARS-CoV-2 testing results are shown in Table 2. Conclusion The CDC MIS-C case definition is intentionally broad. Using national surveillance data, we evaluated case inclusion under narrower criteria, prioritizing features of MIS-C that distinguish it from similar pediatric inflammatory conditions. A surveillance case definition may not capture all cases and is not intended to replace clinical judgment. We plan to assess additional criteria combinations, describe potentially excluded cases, and incorporate findings into a revised definition. Disclosures All Authors: No reported disclosures.