Page created on February 28, 2022. Last updated on March 2, 2022 at 15:57
Introduction and epidemiology
COVID-19 is a pandemic infectious disease which was discovered in the end of 2019 and is still ongoing as of time of writing. It’s caused by the SARS-CoV-2, a novel coronavirus. Different variants have different severity and infectiousness, and at the time of writing, the Omicron variant is the dominating one. Children of all ages can get COVID-19, but they’re generally affected less frequently than adults.
However, COVID-19 in children can cause a severe and life-threatening complication called multisystem inflammatory syndrome in children (MIS-C). MIS-C is a relatively rare complication, affecting <1% of COVID-19 positive children. The syndrome bears resemblance to Kawasaki disease and toxic shock syndrome. It usually develops 2 – 6 weeks after the initial infection. The initial infection is often asymptomatic or unnoticed.
The SARS-CoV-2 virus binds its spike protein (S protein) to the ACE2 protein on host cells. The virus then uses an enzyme called TMPRSS2 to invade the host cell. The virus has direct cytopathic effects, but most of its clinical features and consequences are thought to rather be due to the effects of the immune system.
MIS-C is thought to be due to an abnormal immune response to the SARS-CoV-2 virus.
COVID-19 in children is generally mild (and milder than in adults) unless complications develop. The most common symptoms are fever, cough, shortness of breath, myalgia, and other influenza-like symptoms. A relatively specific symptom is loss of smell or taste.
MIS-C presents with fever (always present, usually persistent), GI symptoms, rash, and conjunctivitis. After a few days they may develop shock or multi organ failure. Myocardial dysfunction is typical.
Diagnosis and evaluation
Diagnosis is based on rapid antigen tests (less sensitive) or PCR tests based on nasopharyngeal swab. Serology can be used to detect prior infection. Elevation of inflammatory markers is typical, as is lymphocytopaenia.
In case of MIS-C, there may be neutrophilia with lymphocytopaenia. Procalcitonin is often elevated despite there being no bacterial focus. Cardiac markers (troponin, BNP) elevation should myocardial dysfunction. If myocardial dysfunction is suspected, echocardiography should be performed.
Only children with severe disease (severe COVID-19 or MIS-C) require hospitalisation. Treatment is mainly symptomatic. Remdesivir (an antiviral), glucocorticoids, and anti-IL-6 receptor antibodies may be used on a case-by-case basis.
Treatment of MIS-C involves stabilisation, possibly including resuscitation if shock develops. Because it may be impossible to distinguish MIS-C from septic shock or toxic shock syndrome in the acute phase, these patients are usually given empiric antibiotics until the latter diagnoses are ruled out. The current mainstay of treatment for MIS-C are IVIG with or without glucocorticoids, and aspirin with or without LMWH.
Vaccines which reduce the risk of both mild and severe disease are available. At the time of writing, the age limit for the vaccine varies from country to country, and it may change. In general, the youngest children (<5 years) are not eligible for the vaccine.
The prognosis of COVID-19 is good. Even in the context of MIS-C, the prognosis is very good as most children have a full clinical recovery. However, in some cases, symptoms like fatigue, cognitive impairment, loss of smell/taste may persist for weeks or months after the infection. The long-term complications of COVID-19 are also not known.