Background The clinical presentation and severity of Multisystem Inflammatory Syndrome in Children associated with COVID-19 (MIS-C) is widespread and presents a very low mortality rate in high-income countries. This research describes the clinical characteristics of MIS-C in critically ill children in middle-income countries and the factors associated with the rate of mortality and patients with critical outcomes. Methods An observational cohort study was conducted in 14 pediatric intensive care units (PICUs) in Colombia between April 01, 2020, and January 31, 2021. Patient age ranged between one month and 18 years, and each patient met the requirements set forth by the World Health Organization (WHO) for MIS-C. Results There were seventy-eight children in this study. The median age was seven years (IQR 1-11), 18 % (14/78) were under one year old, and 56 % were male. 35 % of patients (29/78) were obese or overweight. The PICU stay per individual was six days (IQR 4-7), and 100 % had a fever upon arrival to the clinic lasting at least five days (IQR 3.7-6). 70 % (55/78) of patients had diarrhea, and 87 % (68/78) had shock or systolic myocardial dysfunction (78 %). Coronary aneurysms were found in 35 % (27/78) of cases, and pericardial effusion was found in 36 %. When compared to existing data in high-income countries, there was a higher mortality rate observed (9 % vs. 1.8 %; p=0.001). When assessing the group of patients that did not survive, a higher frequency of ferritin levels was found, above 500 ngr/mL (100 % vs. 45 %; p=0.012), as well as more cardiovascular complications (100 % vs. 54 %; p = 0.019) when compared to the group that survived. The main treatments received were immunoglobulin (91 %), vasoactive support (76 %), steroids (70.5 %) and antiplatelets (44 %). Conclusions Multisystem Inflammatory Syndrome in Children due to SARS-CoV-2 in critically ill children living in a middle-income country has some clinical, laboratory, and echocardiographic characteristics similar to those described in high-income countries. The observed inflammatory response and cardiovascular involvement were conditions that, added to the later presentation, may explain the higher mortality seen in these children.

<b><i>Background:</i></b> Histopathological analysis can provide additional clues in COVID-19 understanding. During the last year, autopsy reports have revealed that diffuse alveolar damage (DAD) is the most significant observed finding. The aim of this study is to review cases in the literature about COVID-19 autopsies that reported microthrombi in different organs. <b><i>Methods:</i></b> We performed a systematic literature review in PubMed, Virtual Health Library (VHL), and Google Scholar. <b><i>Results:</i></b> In total, 151 autopsies were included, and 91 cases presented microthrombi in the lung (73%), heart (11.2%), kidney (24%), and liver (16.3%). The age range was between 27 and 96 years. Males were 64.8%. The patients with microthrombi had more comorbidities such as arterial hypertension (62%), obesity or overweight (64%), diabetes mellitus type 2 (51%), and heart disease (53%). The most common histopathological changes found in patients with lung microthrombosis were DAD in exudative phase (78%), pulmonary embolism (59%), and lung infarct (81%). Presence of microthrombi was associated with arterial hypertension (<i>p</i> &#x3c; 0.0001) and DAD in exudative and proliferative phases (<i>p</i> = 0.02). <b><i>Discussion:</i></b> The analysis of these results shows that microthrombi in COVID-19 autopsies may be found in different organs and are more frequent in patients with comorbidities, pulmonary embolism, and lung infarct.

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