The pathogenesis is not completely known and could implicate several factors. SARS-CoV-2 could have one of several roles; it could act as an environmental trigger for the condition either directly or indirectly (by somehow paving the way for a different trigger). As with Kawasaki disease, antibody-dependent enhancement, whereby development of antibodies could facilitate viral entry into host cells, has been proposed as a potential mechanism. Epidemiological considerations make a post-infectious mechanism seem likely, possibly coinciding with the development of acquired immune responses to the virus. It has been suggested that the condition may be caused by the cytokine storms induced by COVID-19. The characteristic ability of coronaviruses to block type I and type III interferon responses could help explain a delayed cytokine storm in children whose immune systems struggle to control SARS-CoV-2 viral replication, or are overwhelmed by a high initial viral load. One plausible chain of events leading up to a hyperimmune response could involve early viral triggering of macrophage activation, followed by T helper cell stimulation, in turn leading to cytokine release, stimulation of macrophages, neutrophils, and monocytes, in conjunction with B cell and plasma cell activation, and autoantibody production. It is unknown to what extent the pathophysiology resembles that of other paediatric inflammatory syndromes that share similar clinical features. Clinical overlaps with syndromes that have different causes (Kawasaki disease, toxic shock, macrophage activation syndrome, and secondary haemophagocytic lymphohistiocytosis) may be explained by immunological activation and dysregulation of similar inflammatory pathways. In each of these syndromes, a cytokine storm leads to failure of multiple organs. They also share with MIS-C and severe cases of COVID-19 high levels both of ferritin (released by neutrophils) and of haemophagocytosis. The frequent gastrointestinal presentation and mesenteric lymph node inflammation are in keeping with the known liking of SARS-CoV-2 to replicate in enterocytes. Association of Kawasaki-like disease with COVID-19 could support the view that SARS-CoV-2 can cause systemic vasculitis by targeting endothelial tissue via angiotensin-converting enzyme 2 (ACE2), the protein which the virus uses to gain access to cells. While the initial infection is known to be capable of causing acute myocardial damage, occurrence of myocarditis could also plausibly be linked to systemic hyperinflammation triggered by a disorderly post-infectious immune response. It has been suggested that SARS-CoV-2 might lead to immune-mediated damage to the heart and coronary arteries via immune complexes or increased T-cell responses. Understanding the pathophysiology is a key research priority. Questions regarding the underlying molecular mechanisms that lead to the disorder following exposure to SARS-CoV-2 include identification of: any genetic predisposition factors; any associations with particular viral variant/s; any molecular patterns capable of triggering the autoimmune/autoinflammatory responses. Another key question is whether the molecular mechanisms that trigger autoimmune/autoinflammatory responses in children with PMIS and adults with severe COVID-19 (including the induction of high concentrations of IL-6) are similar or distinct. A potential link with Kawasaki disease is under discussion. 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.
Multisystem inflammatory syndrome in children
Kawasaki disease
Cutaneous manifestations of COVID-19
Systemic inflammatory response syndrome
Chest pain in children
complications of Typhus
Multiple organ dysfunction syndrome
complications of Sepsis