Coronavirus disease 2019 (COVID-19) is responsible for significant lung disease in adults. Despite mild manifestations in most children, multisystem inflammatory syndrome (MIS-C) associated with COVID-19 is well described in older children with cardiac manifestations. However, MIS-C-related cardiac manifestations are not as well described in younger children.

The study is a retrospective analysis of MIS-C patients under the age of 5 years admitted between May and November 2020 to a single centre. Included cases fulfilled the case definition of MIS-C according to Royal College of Pediatrics and Child Health criteria with laboratory, electrocardiogram, or echocardiographic evidence of cardiac disease. Collected data included patients’ demographics, laboratory results, echocardiographic findings, management, and outcomes.

Out of 16 MIS-C cases under 5 years of age, 10 (62.5%) had cardiac manifestations with a median age of 12 months, 9 (90%) were previously healthy. Cardiac manifestations included coronary arterial aneurysms or ectasia in five (50%) cases, two (20%) with isolated myopericarditis, coronary ectasia with myocarditis in two (20%), and supraventricular tachycardia in one (10%). Intravenous immunoglobulins were given in all cases with coronary involvement or myocarditis. The median duration of hospitalisation was 7 (6–14) days; two (20%) cases with cardiac disease were mechanically ventilated and mortality in MIS-C cases below 5 years was 12.5%. Normalisation of systolic function occurred in half of the affected cases within 1 week and reached 100% by 30 days of follow-up.

MIS-C associated with SARS-CoV-2 has a high possibility of serious associated cardiac manifestations in children under the age of 5 years with mortality and/or long-term morbidities such as coronary aneurysms even in previously healthy children.