COVID-19 and multisystem inflammatory syndrome in children: Case

This school-age child has the signature presentation of multisystem inflammatory syndrome in children: persistent fever with multiorgan involvement, shock, and a SARS-CoV-2 exposure three weeks earlier. The negative nasopharyngeal polymerase chain reaction is expected because the syndrome is post-infectious, and her immunoglobulin G serology will be positive. Her elevated troponic and her shock place cardiac involvement at the centre of management, and the echocardiogram is the pivotal next investigation. [1]

Clinical findings

The key findings are the persistent fever with multiorgan involvement, the shock with delayed capillary refill and hypotension, the mucocutaneous features of conjunctivitis and red cracked lips, and the elevated troponic signalling cardiac involvement. The markedly raised C-reactive protein and ferritin confirm severe inflammation. The differential is bacterial sepsis, Kawasaki disease with coronary involvement, toxic shock syndrome, and a surgical abdomen given the abdominal pain, but the temporal relationship to a household COVID-19 illness two to six weeks earlier and the multiorgan pattern make multisystem inflammatory syndrome the working diagnosis. [1]

The echocardiogram is mandatory and assesses left and right ventricular function, valve regurgitation, pericardial effusion, and the coronary arteries with Z-scores. In a cardiac-dominant phenotype the combination of depressed left ventricular function and coronary arteritis drives management, and the finding of a coronary aneurysm would add therapeutic anticoagulation to the plan. The inflammatory and coagulation panel confirms a markedly raised D-dimer consistent with the prothrombotic state. [2]

Management

Resuscitation follows an airway, breathing, circulation approach with two MIS-C-specific refinements. Give high-flow oxygen and establish intravenous access. Treat the shock with cautious 10 millilitres per kilogram boluses of 0.9 per cent sodium chloride, reassessing after each and titrating to perfusion, because capillary leak and cardiac dysfunction mean that over-resuscitation worsens pulmonary oedema. Move early to vasoactive support with epinephrine for her cold shock, and give empiric broad-spectrum antibiotics while sepsis is excluded. [2]

Once the diagnosis is established and she is stable, begin immunomodulation. First-line therapy is intravenous immunoglobulin 2 grams per kilogram over 12 to 24 hours PLUS corticosteroids as methylprednisolone pulses or prednisolone, because the combination improves outcomes and shortens fever compared with immunoglobulin alone. Add low-dose aspirin at 3 to 5 milligrams per kilogram per day for its antiplatelet effect. If the echocardiogram shows a coronary aneurysm with a Z-score of 5 or more, a documented thrombus, or a left ventricular ejection fraction under 35 per cent, add therapeutic anticoagulation. For refractory shock add anakinra or infliximab. [3]

She is admitted to the paediatric intensive care unit for shock and cardiac involvement under a multidisciplinary team of cardiology, infectious diseases, and rheumatology. Defervescence usually occurs within 24 to 48 hours of immunomodulation, and the response is itself reassuring. [3]

Complications and follow-up

Cardiac complications are the chief driver of morbidity and mortality in multisystem inflammatory syndrome. Coronary artery aneurysms are present in roughly 15 to 20 per cent at diagnosis, and although many regress with treatment, a minority persist and dictate long-term follow-up. Myocardial dysfunction, arrhythmia, valvulitis, and acute heart failure all feature, and mortality overall is approximately 1 to 2 per cent, concentrated in children presenting in shock with cardiac dysfunction. [1]

Her follow-up centres on the coronary arteries. A serial echocardiogram is performed at one to two weeks and again at four to six weeks, with additional imaging guided by cardiology, and cardiac magnetic resonance imaging is used in selected cases for late myocardial and coronary assessment. She is restricted from vigorous exercise during recovery, and persistent coronary changes drive long-term cardiovascular surveillance. Counsel the family that the recent COVID-19 illness triggered an over-reaction of her immune system, that the treatment quiets that response, and that the main long-term question is the coronary arteries, which is why the echocardiogram is repeated. Provide a clear safety-net for re-presentation. [2]