The RCPCH initially outlined a provisional approach to clinical management, including guidance on early medical management, monitoring and some general principles of treatment; for the UK, consensus has since been reached regarding a recommended pathway for clinical management (including access to registered clinical trials). The National Institutes of Health provides some general considerations. The American College of Rheumatology provides guidance for clinical management of MIS-C. The American Academy of Pediatrics has also provided some interim guidance. Other proposals have also been made. RCPCH guidance recommends that all affected children should be treated as having suspected COVID-19.Little specific information is available regarding therapeutic effectiveness. Most children who have been treated as for Kawasaki disease have recovered. Supportive care is a mainstay of therapy, and for mild or moderate disease it may be sufficient. Major complications may respond well to more aggressive supportive care. Cardiac and respiratory support may benefit children who present predominantly with shock.Strategies for clinical management tend to be broadly based on anti-inflammatory medications, treatment of shock, and prevention of thrombosis. Most children have received immunomodulatory treatment with intravenous immunoglobulin (IVIG). IVIG has been reported target IL-1β+ neutrophils and their activation in the affected children. Other anti-inflammatory treatments have been used, including corticosteroids at various doses. Good responses have been recorded for IVIG, with or without corticosteroids. Cases requiring steroids due to resistance to IVIG may be more common than in Kawasaki disease.
The time the syndrome takes to appear following the initial viral infection is debated, though it may develop between the first and second week. Epidemiological data suggest that recognition of the disease may typically be delayed by 2–6 weeks, and usually by 3–4 weeks. By the time of presention, children have often developed antibodies to SARS-CoV-2, but test negative for the virus at RT-PCR.The condition may match some or all of the diagnostic criteria for Kawasaki disease (i.e. the complete or incomplete/atypical subtypes), or for Kawasaki disease shock syndrome. It tends to affect all paediatric age groups, ranging from infancy to adolescence. It can also share clinical features with other paediatric inflammatory conditions, including toxic shock syndrome, and secondary haemophagocytic lymphohistiocytosis or macrophage activation syndrome. Coinfections with other pathogens have been recorded.Affected children always present with persistent fever. Other clinical features at presentation vary. In contrast to acute COVID-19, most children have gastrointestinal symptoms, such as diarrhoea, vomiting, and intense abdominal pain (sometimes severe enough to suggest appendicitis). Muscle pain and feelings of tiredness and general physical weakness are also very common. Some Kawasaki-like symptoms that may be present (especially in children under the age of 5) include mucosal changes around the mouth ("strawberry tongue", cracked lips, etc. ), red eyes (conjunctivitis without pus), widespread rash (consistent with leukocytoclastic vasculitis), red or swollen hands and feet, and enlarged lymph nodes. Chest or neck pain may also be present. Severe headache and altered mental state have been reported, along with various neurological disturbances.