COVID-19 and multisystem inflammatory syndrome in children: Viva

Branch 1: Recognising the post-COVID hyperinflammatory emergency

The candidate should immediately recognise that this school-age child with persistent fever, multiorgan involvement (gastrointestinal symptoms, mucocutaneous features, shock), and a SARS-CoV-2 exposure three weeks earlier has multisystem inflammatory syndrome in children until proven otherwise. The key discriminating feature is the temporal relationship: the recent febrile illness two to six weeks earlier is the trigger, and the current presentation is the delayed post-infectious hyperinflammatory phenotype, not acute COVID-19. [1]

The candidate should state that any school-age child with persistent fever and organ dysfunction in the weeks after a COVID-19 illness must be presumed to have multisystem inflammatory syndrome until proven otherwise, and that the first priority is resuscitation of the shock and the early echocardiogram, because cardiac involvement is what makes this condition lethal. The alternative of bacterial sepsis must be covered empirically while the workup proceeds. [1]

Branch 2: Investigations and the echocardiogram decision

The candidate should outline the inflammatory panel: a full blood count showing neutrophilia, lymphopaenia, and thrombocytopaenia; markedly raised C-reactive protein and ferritin; raised fibrinogen, lactate dehydrogenase, and triglycerides; a markedly raised D-dimer; and a low albumin. 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 examiner will probe the SARS-CoV-2 testing. Because the infection was weeks earlier, the nasopharyngeal polymerase chain reaction is often negative and does not exclude the diagnosis; immunoglobulin G serology should be sent and is positive in most children. Blood culture and targeted microbiology exclude sepsis and its mimics. [1]

The candidate must then justify the echocardiogram as the pivotal investigation: it assesses left and right ventricular function, valve regurgitation, pericardial effusion, and the coronary arteries, with coronary dimensions reported as Z-scores. The echocardiogram is performed at diagnosis and repeated serially, because coronary changes can evolve, and the Z-scores drive anticoagulation decisions. [1]

Branch 3: Resuscitation, immunomodulation, and differentiating Kawasaki disease

The candidate should outline cautious resuscitation. Treat the shock with 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: epinephrine for cold shock, norepinephrine for warm shock, rather than escalating fluids when the response is incomplete. Give empiric broad-spectrum antibiotics while sepsis is excluded. [2]

First-line immunomodulation is intravenous immunoglobulin 2 grams per kilogram over 12 to 24 hours PLUS corticosteroids (methylprednisolone pulses or prednisolone), because the combination improves outcomes and shortens fever compared with immunoglobulin alone. Add low-dose aspirin for its antiplatelet effect, and therapeutic anticoagulation if the echocardiogram shows a coronary aneurysm with a Z-score of 5 or more, a documented thrombus, or severe left ventricular dysfunction. For refractory disease, add anakinra or infliximab. [2]

When the examiner probes the distinction from Kawasaki disease, the candidate should state that Kawasaki disease classically affects children under five, produces less shock, and is not temporally linked to SARS-CoV-2, whereas multisystem inflammatory syndrome typically affects school-age children and follows SARS-CoV-2 by two to six weeks. Coronary aneurysms occur in both, which is why the Kawasaki-overlap phenotype of multisystem inflammatory syndrome is managed with the Kawasaki immunoglobulin protocol and heightened coronary surveillance. [3]