This is what the results of a study by researchers from the USP Medical School and the Adolfo Lutz Institute using a minimally invasive autopsy technique indicate

Although Covid-19 is usually mild or asymptomatic in children and adolescents, severe cases can lead to death. To clarify the extent of the disease, changes related to Pediatric Multisystemic Inflammatory Syndrome (SIM-P), and the role of tissue damage induced by the virus, a study was carried out with minimally invasive autopsy guided by ultrasound in five youngsters, from 7 months to 15 years, who died by Covid-19. The research results were published in an article published by the Lancet group's free access scientific journal EClinicalMedicine, on April 25, 2021.

Since the beginning of the pandemic until the end of December 2020, Brazil had registered more than 7.6 million people infected and 193.9 thousand deaths. Among these, 1,203 children and adolescents died from Covid-19. To date, this is the first record of a series of autopsies done on pediatric Covid-19 cases. Tissue samples from all vital organs were analyzed by conventional microscopy, electron microscopy, polymerase chain reaction by reverse transcription (RT-PCR) and immunohistochemistry. SARS-CoV-2 was detected in all patients in the lungs, heart and kidneys and in cells lining the blood vessels of the heart and brain in two patients with SIM-P.

Histological findings varied among patients, including SARS-CoV-2 pneumonia, pulmonary microthrombosis, cerebral edema, inflammation of the heart muscle, and intestinal inflammation. “In addition, we showed for the first time the presence of SARS-CoV-2 in the brain tissue of a child with SIM-P with acute encephalopathy and in the intestinal tissue of a child with acute colitis. Inflammation of cardiac tissue with the presence of the virus had previously been described in one of the cases ”, says Professor Marisa Dolhnikoff, of the Pathology Department at the Faculdade de Medicina da Universidade de São Paulo (FMUSP) and coordinator of the study.

Two main patterns of severe Covid-19 were observed: an acute respiratory disease, a result of severe pneumonia caused by SARS-CoV-2, present in the two children with previous diseases, and pediatric multisystem inflammatory syndrome, with the involvement of various organs and tissues, present in the three previously healthy children.

“SIM-P is considered to be an exacerbated immune reaction in response to previous SARS-CoV-2 infection, but the presence of the virus in different organs, associated with cellular ultrastructural changes, indicates that a direct effect of SARS-CoV-2 in tissues is involved in the pathogenesis of SIM-P ”, says Professor Marisa.

The study found the “high capacity of SARS-CoV-2 to invade and cause damage to the tissues of various organs as one of the factors that induce SIM-P, triggering a variety of clinical manifestations that include, in addition to persistent fever, abdominal pain , heart failure and seizures ”, said Dr. Amaro Nunes Duarte Neto, infectious disease and pathologist at FMUSP and Instituto Adolfo Lutz and one of the main authors of the study.

The researchers also detected the formation of pulmonary microthrombi in children with SIM-P, similar to what had already been observed in adults with Covid-19. Professor Elia Caldini explains that “phenomena related to blood clotting must always be considered at Covid-19, since electron microscopy shows that, in all the organs studied, there are blood capillaries blocked by the accumulation of red blood cells, leukocytes, remains cells and fibrin, including rupture of the endothelial wall. ” These observations have a direct impact on the therapeutic approach of SIM-P.

As the pandemic progresses and more children and adolescents become infected, “it is very important that the medical community be aware of possible clinical manifestations other than Covid-19 in children and adolescents, so that the infection is diagnosed and the treatment of SIM-P with hospital support should be instituted quickly”, says Professor Marisa Dolhnikoff.

The study received support from the São Paulo State Research Support Fund (FAPESP), from the Bill and Melinda Gates Foundation and from the National Council for Scientific and Technological Development (CNPq). The work was developed in the Pathology Department of FMUSP, with the collaboration of researchers from the Institute of Children and Adolescents of Hospital das Clínicas (HC) of FMUSP, of the Laboratory of Clinical and Experimental Gastroenterology (LIM-07) of HCFMUSP, of the University Hospital of USP, from the Anesthesia Division of HCFMUSP, from the Death Verification Service of the Capital (Svoc) and from the Adolfo Lutz Institute.

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Intestine: acute colitis with detection of SARS-CoV-2 by immunohistochemistry (in red)
Brain: electron microscopy of oligodendrocyte surrounded by myelinated axons (asterisks). There is extensive disorganization of the cytoplasm with vesiculation, which is typical of coronavirus infection. Some vesicles (arrows) contain virus-like particles. Detail: enlargement of an intracellular vesicle (the black arrow indicates the membrane) and viral particles consistent in size and shape with the Coronaviridae family (white arrows point to nucleocapsids)