Working Diagnosis:
Multisystem Inflammatory Syndrome in Children (MIS-C)
COVID Sequelae including pro-thrombotic and pro-inflammatory states

Treatment:
He was treated with prophylactic Lovenox due to his elevated D-dimer and risk for VTE. His MIS-C was treated with IVIG 1 g/kg (max 80 g). His inflammatory markers decreased, and he was discharged from the hospital on ASA 81mg.

Outcome:
He clinically improved and his ASA was stopped. He completed a progressive exercise program, which included strict cardiac monitoring over a week, without concerns. He returned to full football activity 4 weeks after his initial diagnosis.

Author's Comments:
Various case reports have been written about MIS-C, but little is known about its impact on athletes and what kinds of return-to-play protocol should be utilized to ensure athlete safety. Multiple prior case series have shown the incidence of myocarditis in patients with MIS-C to be 50% or greater.Another case series of 186 MIS-C patients showed that: 80% received intensive care, 20% received mechanical ventilation, 48% received vasoactive support, 8% had Coronary-artery aneurysms and 2% died.
To miss this diagnosis in a young, otherwise healthy athlete could have devastating consequences. We do not know the negative outcomes that could have occurred in this athlete if it was not for the quick action and initiation of treatment by the athletic training staff and emergency department. This case is an example of a case of MIS-C in a high-level athlete and highlights the importance of early diagnosis and treatment, as well as the various cardiac diagnostic modalities needed to assist with the return-to-play process.

Editor's Comments:
As SARS-CoV 2/COVID infections have been found in otherwise healthy young patients, there has been significant focus on possible sequelae. While MIS-C has been predominantly described in the young pediatric population, the CDC definition includes patients up to 20-years-old. Though MIS-C includes multi-system organ involvement, including cardiac concerns, possible myocarditis in young athletes has received separate significant attention. In hospitalized adults, over 20% of patients had evidence of acute cardiac injury (9). At the collegiate and professional levels, there was initial evidence of a significant prevalence (as high as 15%) of cardiac MRI findings of myocarditis in both asymptomatic patients and those with significant symptoms (10). Once systematic return-to-play cardiac screening guidelines were created for professional athletes, only 4% of athletes who tested positive for COVID-19 had abnormal test results, and less than 1% were found to have pathology (11). At the collegiate level, recent studies showed that amongst nearly 20,000 athletes, 0.5-3% had definite or probable SARS-CoV-2 cardiac involvement, and not a single adverse cardiac event occurred (12). These data indicate that Cardiac MRI is likely better utilized for screening based on symptom burden and initial abnormal lab, EKG, or echo results rather than as an initial screening tool (11).

References:
1. Multisystem Inflammatory Syndrome in Children (MIS-C) Associated with Coronavirus Disease 2019 (COVID-19) Centers for Disease Control and Prevention: Emergency Preparedness and Response: CDC Health Alert Network; 2020 [Available from: https://emergency.cdc.gov/han/2020/han00432.asp.
2. Dean PNJ, Lanier Burns; Paridon, Stephen M. Returning To Play After Coronavirus Infection: Pediatric Cardiologists’ Perspective American College of Cardiology: American College of Cardiology; 2020 [Available from: https://www.acc.org/latest-in-cardiology/articles/2020/07/13/13/37/returning-to-play-after-coronavirus-infection.
3. Cheung EW, Zachariah P, Gorelik M, Boneparth A, Kernie SG, Orange JS, et al. Multisystem Inflammatory Syndrome Related to COVID-19 in Previously Healthy Children and Adolescents in New York City. JAMA. 2020;324(3):294-6.
4. Dufort EM, Koumans EH, Chow EJ, Rosenthal EM, Muse A, Rowlands J, et al. Multisystem Inflammatory Syndrome in Children in New York State. N Engl J Med. 2020;383(4):347-58.
5. Feldstein LR, Rose EB, Horwitz SM, Collins JP, Newhams MM, Son MBF, et al. Multisystem Inflammatory Syndrome in U.S. Children and Adolescents. N Engl J Med. 2020;383(4):334-46.
6. Henderson LA, Canna SW, Friedman KG, Gorelik M, Lapidus SK, Bassiri H, et al. American College of Rheumatology Clinical Guidance for Multisystem Inflammatory Syndrome in Children Associated With SARS-CoV-2 and Hyperinflammation in Pediatric COVID-19: Version 1. Arthritis Rheumatol. 2020;72(11):1791-805.
7. Belhadjer Z, Meot M, Bajolle F, Khraiche D, Legendre A, Abakka S, et al. Acute Heart Failure in Multisystem Inflammatory Syndrome in Children in the Context of Global SARS-CoV-2 Pandemic. Circulation. 2020;142(5):429-36.
8. Kaushik A, Gupta S, Sood M, Sharma S, Verma S. A Systematic Review of Multisystem Inflammatory Syndrome in Children Associated With SARS-CoV-2 Infection. Pediatr Infect Dis J. 2020;39(11):e340-e6.
9. Phelan D, Kim JH, Chung EH. A Game Plan for the Resumption of Sport and Exercise After Coronavirus Disease 2019 (COVID-19) Infection. JAMA Cardiol. Published online May 13, 2020. doi:10.1001/jamacardio.2020.2136
10. Daniels CJ, Rajpal S, Greenshields JT, et al. Prevalence of Clinical and Subclinical Myocarditis in Competitive Athletes With Recent SARS-CoV-2 Infection: Results From the Big Ten COVID-19 Cardiac Registry. JAMA Cardiol. Published online May 27, 2021.
11. Martinez MW, Tucker AM, Bloom OJ, et al. Prevalence of Inflammatory Heart Disease Among Professional Athletes With Prior COVID-19 Infection Who Received Systematic Return-to-Play Cardiac Screening. JAMA Cardiol. Published online March 04, 2021.

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