COVID-19 and multisystem inflammatory syndrome in children: SAQ

This school-age child has the signature presentation of multisystem inflammatory syndrome in children: persistent fever with multiorgan involvement (gastrointestinal symptoms, mucocutaneous features, shock), markedly raised inflammatory markers, an elevated troponin, and a SARS-CoV-2 exposure three weeks earlier. His delayed capillary refill, tachycardia, and hypotension indicate early shock, and the elevated troponic signalling cardiac involvement makes the echocardiogram the pivotal next investigation. [1]

Question 1 (10 marks)

Outline your diagnostic approach including the key investigations and their interpretation in this child. [1]

The diagnosis of multisystem inflammatory syndrome in children rests on persistent fever, laboratory evidence of inflammation, multiorgan involvement, and current or recent SARS-CoV-2 infection or exposure with no alternative diagnosis. This child meets the clinical criteria on persistent fever, gastrointestinal and mucocutaneous involvement, and shock, with a temporally related SARS-CoV-2 exposure three weeks earlier. [1]

Send the full inflammatory and cardiac panel: a full blood count, which typically shows neutrophilia, lymphopaenia, and thrombocytopaenia; C-reactive protein, ferritin, fibrinogen, lactate dehydrogenase, and triglycerides, all markedly raised; coagulation studies including a markedly raised D-dimer; albumin, which is typically low; and electrolytes, with hyponatraemia common. The cardiac biomarkers are pivotal: troponin and B-type natriuretic peptide or its N-terminal propeptide define cardiac involvement and guide the intensity of monitoring and the escalation of immunomodulation. [1]

The SARS-CoV-2 testing requires care because the infection was weeks earlier. A negative nasopharyngeal polymerase chain reaction is expected and does not exclude the diagnosis; immunoglobulin G serology should be sent and is positive in most children, supporting the post-infectious mechanism. Blood culture and targeted microbiology exclude sepsis and its mimics. An electrocardiogram screens for arrhythmia and conduction abnormality. [1]

The echocardiogram is mandatory and is the test that most directly changes management: it assesses left and right ventricular function, valve regurgitation, pericardial effusion, and the coronary arteries, with coronary dimensions reported as Z-scores so that aneurysms are detected against age-appropriate norms. In this child the elevated troponic signals myocardial involvement, so the echocardiogram is urgent. [1]

Question 2 (10 marks)

Describe your initial management including resuscitation and immunomodulation. [2]

Begin with an airway, breathing, circulation approach. This child is in early shock: give high-flow oxygen, establish intravenous access, and treat the shock with cautious fluid boluses of 10 millilitres per kilogram of 0.9 per cent sodium chloride, reassessing after each and titrating to perfusion. Because capillary leak and cardiac dysfunction coexist in multisystem inflammatory syndrome, over-resuscitation risks worsening pulmonary oedema, so the total fluid is modest and the child is watched for hepatomegaly and a rising oxygen need. [2]

Move to early vasoactive support rather than escalating fluids when the response is incomplete. In this child, who has poor perfusion and a narrow pulse pressure with likely depressed left ventricular function, epinephrine is the agent for cold shock. Give empiric broad-spectrum antibiotics while sepsis is being excluded, because MIS-C and bacterial sepsis are indistinguishable at presentation, and correct electrolyte disturbances. [2]

Once the diagnosis is established and the child is stable, begin immunomodulation. First-line therapy is intravenous immunoglobulin 2 grams per kilogram over 12 to 24 hours PLUS corticosteroids, given as methylprednisolone pulses of 10 to 30 milligrams per kilogram per day for three days or as oral prednisolone at 1 to 2 milligrams per kilogram per day, because combining them 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. [3]

Arrange paediatric intensive care admission for shock and cardiac involvement, with a multidisciplinary team including cardiology, infectious diseases, and rheumatology. If shock is refractory to first-line therapy, add an adjunctive biologic such as anakinra, the interleukin-1 receptor antagonist, at 4 to 6 milligrams per kilogram per day, or infliximab. Plan serial echocardiography at one to two weeks and four to six weeks to monitor the coronary arteries, and restrict vigorous exercise during recovery. [3]