Acute respiratory distress syndrome (ARDS) followed by repair with lung remodeling is observed in COVID-19. These findings can lead to pulmonary terminal fibrosis, a form of irreversible sequelae. There is evidence that TGF-β is intimately involved in the fibrogenic process. When activated, TGF-β promotes the differentiation of fibroblasts into myofibroblasts and regulates the remodeling of the extracellular matrix (ECM). In this sense, the present study evaluated the histopathological features and immunohistochemical biomarkers (ACE-2, AKT-1, Caveolin-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-β1 tissue expression) involved in the TGF-β1 signaling pathways and pulmonary fibrosis. The study consisted of 24 paraffin lung samples from patients who died of COVID-19 (COVID-19 group), compared to 10 lung samples from patients who died of H1N1pdm09 (H1N1 group) and 11 lung samples from patients who died of different causes, with no lung injury (CONTROL group). In addition to the presence of alveolar septal fibrosis, diffuse alveolar damage (DAD) was found to be significantly increased in the COVID-19 group, associated with a higher density of Collagen I (mature) and III (immature). There was also a significant increase observed in the immunoexpression of tissue biomarkers ACE-2, AKT-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-β1 in the COVID-19 group. A significantly lower expression of Caveolin-1 was also found in this group. The results suggest the participation of TGF-β pathways in the development process of pulmonary fibrosis. Thus, it would be plausible to consider therapy with TGF-β inhibitors in those patients recovered from COVID-19 to mitigate a possible development of pulmonary fibrosis and its consequences for post-COVID-19 life quality.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19, spread rapidly across the globe in 2020, with most countries experiencing two distinct waves of infection. In Brazil, the second wave was marked by the emergence of the P.1 (Gamma) variant, which disproportionately affected younger individuals and was associated with increased mortality. This study aimed to evaluate the epidemiological profile and post mortem histopathological lung findings, correlate them with laboratory results, and compare the first and second waves of COVID-19. To investigate neutrophil extracellular traps (NETs), we performed immunohistochemistry for citrullinated histone H3 (cit-H3) and myeloperoxidase (MPO). Our cohort included patients who died in the intensive care unit (ICU) of a single center in southern Brazil. The study included 42 patients, 24 from the first wave and 18 from the second, who died between March 2020 and August 2021. Laboratory data included complete blood counts and D-dimer levels. Histopathological analyses were conducted using H&E-stained slides and reviewed independently by two blinded pathologists. MPO and cit-H3 immunohistochemistry were performed to evaluate NETs markers. All cases exhibited varying degrees of inflammation and diffuse alveolar damage (DAD), with frequent microvascular thrombi. Neutrophilic infiltration was significantly higher in the second wave. Additionally, cases with intense neutrophilic infiltration showed a stronger association with thrombosis. NETs were identified in 10 cases. No significant correlation was found between histopathological findings, NETs, and laboratory blood count results. The histopathological findings were consistent with those reported globally. The second wave of COVID-19 showed higher neutrophilic infiltrate in the lung tissue. Neutrophils play a key role in the inflammatory response and NET formation might indicate an increased risk of mortality. Further studies can consider NET-targeted therapies as potential strategies.

Diffuse dermal angiomatosis is a rare vascular disorder of skin tissue in the spectrum of cutaneous reactive angiomatosis. Clinically, it presents as violaceous plaques that may ulcerate and is characterized by endothelial proliferation within the dermis on microscopic examination. It is mainly located in the breasts and extremities. Case Presentation: We report a case of erythematoviolaceous cutaneous plaques in an uncommon location (abdomen and dorsum) in a patient with rheumatoid arthritis and without other disorders such as atherosclerotic disease, macromastia and smoking. Discussion and Conclusion: It is believed that ischemia or inflammation creates local hypoxia, leading to an increase in pro-angiogenic cytokines with subsequent endothelial proliferation and neovascularization. We report a case of a patient with rheumatoid arthritis (autoimmune disease) who presented with an asymptomatic cutaneous violaceous and roundish lesion in the trunk that may be related to diffuse dermal angiomatosis.

COVID-19 severity is frequently linked to exacerbated inflammation, with the inflammasome pathway playing a key role in activating inflammatory interleukins. This observational post-mortem study evaluated the expression of inflammasome-associated molecules in patients who died from COVID-19 during the second wave. Minimally invasive autopsies were performed on patients from the first (n = 24) and second (n = 18) waves. Lung tissue samples underwent immunohistochemical staining for ACE-2, TLR-4, NF-κB, TNF-α, NOX4, NLRP3, ASC, CASPASE-1, IL-1β, IL-18, GSDMD, and CASPASE-9. Additionally, genetic polymorphisms within inflammasome-related genes were assessed via real-time polymerase chain reaction. Lung tissue expressions of TLR-4, NLRP3, and IL-18 were significantly higher in patients from the second wave compared to those from the first, with expression levels of 26.3 versus 12.1, 13.9 versus 6.4, and 25.6 versus 3.8, respectively. The A allele at rs4648090 of NFKB1 and the T allele at rs317155 of NOX4 were associated with increased corresponding protein expression by factors of 5.1 and 8.9, respectively. Notably, IL-18 demonstrated substantial immunological relevance, correlating strongly with elevated expression linked to these genetic variants in second wave cases. These findings suggest that the inflammasome pathway harbors biologically meaningful molecules implicated in severe COVID-19, meriting further investigation for their potential as diagnostic or therapeutic targets.