Features of meningitis have been reported as well as septic encephalopathy, stroke, and Guillain-Barre Syndrome. Some patients present with very low blood pressure and shock, and they may require urgent admission to a paediatric intensive care unit.Cardiovascular involvement is very frequent. Acute heart failure is common in the form of left ventricular dysfunction, and a left ventricular ejection fraction under 60% is frequent. Shock is often of myocardial – mainly left ventricular – origin. Respiratory symptoms are less common, and are not usually a prominent feature. When present, breathing difficulties are often linked to shock, and are suggestive of heart failure. Some children display features of a cytokine storm, including extremely high serum interleukin-6 (IL-6) levels, and need inotropic support to maintain cardiac output. Coronary artery abnormalities, such as dilatation, are frequent. Some children have developed coronary artery aneurysms. Electrocardiographic (ECG) abnormalities are common. Other cardiological features sometimes include inflammation of the heart valves (valvulitis) and of the fibrous sac surrounding the heart (pericarditis). Echocardiographic features of myocarditis (inflammation of the heart muscle) have been recorded.Affected children consistently show laboratory evidence of hyperinflammation. Pronounced biological markers of inflammation generally include strongly raised erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), procalcitonin, ferritin, and IL6. Low platelet counts and impaired blood clotting (coagulopathy) are also common, with  increased levels of D-dimer and fibrinogen. Other haematological features include raised numbers of white blood cells (leukocytosis), characterized by high numbers of neutrophils, with many immature forms, and low numbers of lymphocytes (lymphopaenia).
It has been noted that a leading hypothesis for the pathogenesis of Kawasaki disease also involves a hyperinflammatory response to viral infection (such as by a novel RNA virus) in some genetically predisposed children, and that SARS-CoV-2 is now "added to the list" of implicated viral triggers. Hopes have been expressed that study of the new condition may help understand the hidden mechanisms behind Kawasaki disease. But current evidence suggest that MIS-C and Kawasaki disease represent two distinct disease entities

Proposed role of the STING pathway
A possible role of the stimulator of interferon genes known as STING has been proposed. SARS-CoV-2 is capable of upregulating the STING protein (encoded by TMEM173 transmembrane protein, and expressed in alveoli, endothelial cells, and the spleen), resulting in massive release of interferon-beta and cytokines derived from activation of NF-κB and IRF-3. In MIS-C, such a scenario could lead to a clinical picture similar to STING-associated vasculopathy with onset in infancy (also known as SAVI) – a condition characterized by fever, lung injury, vascular inflammation, myositis, skin lesions (occasionally acral necrosis), and arterial aneurysms. Variations in the presentation and severity of MIS-C might at least partially be explained by characteristic differences in polymorphisms of TMEM173 found in various populations. Epidemiology
Epidemiological information is limited, and clinical statistics currently derive from review of case series. This emerging condition is considered rare. Its incidence is not known.