It is known that at children of COVID-19 usually proceeds easily. However in rare instances children can have a heavy current, and clinical manifestations to differ from adults. In April, 2020 messages about existence at children of a picture of a disease similar to an incomplete syndrome of Kawasaki or toxic shock appeared. Since then the number of messages about children with a similar syndrome around the world grows. The syndrome was called "multisystem inflammatory a syndrome at children" (MVS at children; it is also called by the pediatric multisystem inflammatory syndrome (PMIS). In this article the epidemiology, clinical manifestations, diagnostics and treatment of MVS at children will be considered.
In spite of the fact that the frequency of emergence of MVS at children is unknown, it is possible to assume that this rare complication of COVID-19. The very first reports on MVS at children began to arrive from Great Britain in April, 2020. Since then messages about children with similar symptoms from other parts of the world, including Europe, Canada and the USA are described.
From the clinical point of view most of children with MVS correspond to criteria of the full or incomplete syndrome of Kawasaki (SK). Nevertheless, MVS epidemiology at children differs from classical SK. The regularity which is revealed on the basis of the description of a series of cases is that the majority of cases of MVS at children are observed at children of advanced age and teenagers and also arises against the background of full health. Proceeding from models, it is represented that between the peak of incidence of COVID-19 and peak of cases of MVS at children the delay in several weeks is observed. This lag in three-four weeks coincides with a heating-up period of immunity and assumes that MVS at children can represent a postinfectious complication of a disease, but not an acute infection, at least, at some children.
MVS pathophysiology is completely not found out from children. It is supposed that the syndrome is result of an abnormal immune response on a virus, with some similarities to a syndrome of Kawasaki, the syndrome of activation of macrophages (SAM) and a syndrome of release of cytokines. Mechanisms by means of which SARS-CoV-2 causes an abnormal immune response are unknown. It is supposed that it is the postinfectious process based on terms of growth of emergence of cases concerning COVID-19 peak as it was discussed above. Most of sick children had negative takes of testing for SARS-CoV-2 by method the polymerase chain reaction (PCR), but at the same time a positive serology that also confirms opinion that MVS at children arises after end of an acute phase of an infection. Nevertheless, at some children positive takes of PTsR-testing are revealed. Understanding of mechanisms of an excess immune response at MVS at children is active area of researches.
In the analysis of clinical picture MVS children in available reports on cases had a similar clinical picture of a disease and was shown by the following symptoms:
• constant fever (the average duration is 4 days);
• symptoms from a GIT (an abdominal pain, vomiting, diarrhea);
• symptoms from central nervous system (a headache, slackness, confusion of consciousness);
• respiratory symptoms;
• conjunctivitis;
• damage of mucous membranes;
• pharyngalgia;
• puffiness of hands/legs.
Gastrointestinal symptoms (abdominal pain, vomiting, diarrhea) were the most widespread and expressed, at some children imitating an appendicitis picture. At some children the terminal ileitis at visualization of an abdominal cavity was noted and/or colitis at a kolonoskopiya. Many patients suffered from fever within three-five days then at them "warm shock" developed (distributive shock: the increased warm emission, low general vascular resistance). At some patients fever had shorter period. Shock was often unreceptive to infusional therapy, and demanded introduction of vazopressor and, in certain cases, mechanical support of blood circulation. In most cases damage of lungs was uncharacteristic though oxygen therapy or ventilation with positive pressure for stabilization of a cardiovascular system was required for many children. Respiratory symptoms (hurried breathing, the complicated breath) were most often caused by strong shock. Cough was observed seldom.
The forecast of MVS at children uncertain, considering that it is a new nosological form and our understanding of a disease is still incomplete. Though MVS has much in common with the syndrome of Kawasaki (SK) and toxic shock, it is obvious that disease of MVS at children can be heavier, at the same time many children need an intensive care. Most of children survive, but several cases of death were registered.
Treatment of MVS at children represents a difficult task and will be considered in separate article.