The question of COVID-19 and long-COVID-19 course in children remains unsolved. This infection in children, which is associated with COVID-19, can vary from asymptomatic to systemic damage of various systems. Multisystem inflammatory syndrome in children, associated with SARS-CoV-2 (MIS-C), is a serious condition in children and adolescents after experiencing COVID-19. Published data on MIS-C have indicated that the inflammation can be registered in the gastrointestinal tract (60–100%), as well as in cardiovascular (80%), nervous (29–58%), and respiratory (21–65%) systems. However, with the changing characteristics of SARS-CoV-2, the manifestations of COVID-19 and long-COVID-19 in children have also been changing. Currently, there is no clear understanding of the development of severe COVID-19 and MIS-C in children, especially after being exposed to patients with COVID-19. We presented two new clinical courses of multisystem inflammatory syndrome in children with severe multisystem damage after close contact to relatives with COVID-19 or long-COVID-19. Thus, high-risk children, who are positive for SARS-CoV-2 infection after contact with COVID-19 patients, should be clinically managed during the first few months. The identification of the disease complexity requires the involvement of neurologists, cardiologists, and other specialists.

Arrhythmogenic cardiomyopathy (ACM) is a progressive disease with a high risk of sudden cardiac death (SCD), which is very rare in the pediatric population. Aim. To study the clinical course, outcomes and prognosis in various ACM phenotypes in pediatric patients.Material and methods. During the initial selection, 144 publications were found in the PubMed database. From the initially identified results, an analysis of 7 works was carried out.Results. Positive family history for ACM was revealed in 90% of cases. Every second patient had symptoms of the disease (49,2% (95% confidence interval (CI): 19,3-79,1)). Frequent clinical manifestations of ACM were palpitations, heart failure symptoms, and syncope. The incidence of SCD and sudden cardiac arrest was 7,1% (95% CI: 1,7-12,4) and 5,1% (95% CI: 1,5-8,7), respectively. Implantation of an implantable-cardioverter defibrillator was performed in 40% of cases. Conclusion. We did not reveal any specificity of clinical signs depending on ACM phenotype. However, an earlier onset and an unfavorable course are characteristic of non-classical ACM types. ACM is characterized by a high risk of SCD, so it is extremely important to make a timely diagnosis.

Arrhythmogenic cardiomyopathy is a genetically determined disease of the heart muscle, characterized by fibrofat replacement of the ventricular myocardium, which predisposes to ventricular arrhythmias and a high risk of SCD. Initially, it was believed that this disease is characterized by an exclusive or predominant lesion of the right ventricle. However, fibro-fatty replacement can also be localized in the left ventricle without involvement of the right chambers. This article presents a rare clinical case of a child with Carvajal syndrome with the classic triad of signs (left-dominant form of AСM, keratoderma, and woolly-curly hair).

Arrhythmogenic cardiomyopathy (ACM) is a rare genetic disease characterized by the development of life-threatening ventricular arrhythmias and impaired ventricular systolic function due to fibrofatty infiltration of the myocardium. Currently, the Task Force 2010 criteria and the Padua criteria are proposed for the diagnosis of this disease. However, despite the multiparametric approach, there are certain limitations of the presented algorithms for disease establishment, especially in children. Carrying out such high-tech diagnostic methods as endomyocardial biopsy and magnetic resonance imaging is extremely difficult in the pediatric population. In this regard, the study and application of electrocardiography becomes extremely relevant in children. In addition, there are no data on the features of ventricular arrhythmias in ACM in the pediatric population. In this systematic review with meta-analysis, we studied the features of ventricular arrhythmias and electrocardiographic parameters in various ACM types.

The advent of the COVID-19, specialists are increasingly encountering previously unknown pathological conditions in their practice. For some time, we have believed that COVID-19 in children is most often mild and asymptomatic. However, with the passage of time and the accumulation of the experience, it became obvious that the new infectious disease it will be quite severe in children. Differential diagnosis of multiple organ disorders in children during the COVID-19 pandemic should be primary carried out with the Multisystem Inflammatory Syndrome in Children, associated with COVID-19 (MIS-C), as well as Long-COVID-19. According to published data, the manifestations of these conditions are due to frequent lesions of the gastrointestinal tract (60–100 %), cardiovascular (80 %), nervous (29–58 %) and respiratory (21–65 %) systems. At present, there is no exact idea of these pathological conditions, the criteria for their diagnosis and the tactics of managing children, not only at the stage of diagnosis, but also at the stage of observation. The authors present a diagnostically complex clinical case describing the development of multiple organ damage in a 7-year-old child after contact with a mother who was sick with COVID-19. The data on the course features, the results of the examination and the difficulties of differential diagnosis of this case with other diseases with a similar clinic are summarized.