Aim of the study:
Description of the severe and critical clinical course of COVID-19 in children.

Material and methods:
There is descriptive, single-centered, cross sectional study with recruited of 16 children of severe and critical COVID-19 aged from 1 month till 17 years with hypoxic respiratory failure (8) and multisystem inflammatory syndrome in children (8). The study included of detailed information in period from the manifestation of the disease and hospitalization, the main clinical manifestations at admission to PICU, length of stay, comorbidity and outcomes.

Results:
Severe course and complications of SARS-CoV-2 infection among 16 children for the one year cross period were reported. Comorbid conditions were noted in 62.5% children. The two deceased children had only anemia, which was not diagnosed before admission. The underlying conditions were: mental retardation, epilepsy, severe obesity, congenital brain malformations, cerebral palsy, congenital heart diseases, anemic, bronchopulmonary dysplasia, adrenoleukodystrophy, Down syndrome and subinfections such as acute herpetic encephalitis, salmonellosis, chronic hepatitis B. Four children have died due to acute respiratory failure (3) and pulmonary thrombosis (1). Indicators of activity of inflammation and coagulopathy did not differ in them from children who survived.

Conclusions:
Different comorbid states are associated with severe COVID-19 in children, but the data on specific conditions is limited. Knowledge of comorbid conditions in children that increase the risk of severe or critical course of COVID-19 allows to define the optimum measures of epidemiological control in such children and to modulate the therapy from the onset of the infectious disease. Children without underlying medical conditions may develop severe and critical COVID-19 and require additional supervision or medical attention. More clinical research should be done on pediatric population with critical and severe SARS-CoV-2 infection in other countries.