Chilblains and COVID-19: why SARS-CoV-2 endothelial infection is questioned. Reply from the authors

Mechanism of COVID-19-Induced Cardiac Damage from Patient, In Vitro and Animal Studies

PURPOSE OF REVIEW

Though patient studies have been important for understanding the disease, research done in animals and cell culture complement our knowledge from patient data and provide insight into the mechanism of the disease. Understanding how COVID causes damage to the heart is essential to understanding possible long-term consequences.

RECENT FINDINGS

COVID-19 is primarily a disease that attacks the lungs; however, it is known to have important consequences in many other tissues including the heart. Though myocarditis does occur in some patients, for most cases of cardiac damage, the injury arises from scarring either due to myocardial infarction or micro-infarction. The main focus is on how COVID affects blood flow through the coronaries. We review how endothelial activation leads to a hypercoagulative state in COVID-19. We also emphasize the effects that the cytokine storm can directly have on the regulation of coronary blood flow. Since the main two cell types that can be infected in the heart are pericytes and cardiomyocytes, we further describe the known effects on pericyte function and how that can further lead to microinfarcts within the heart. Though many of these effects are systemic, this review focuses on the consequences on cardiac tissue of this dysregulation and the role that it has in the formation of myocardial scarring.

Interfering with Interferons: A Critical Mechanism for Critical COVID-19 Pneumonia

Infection with SARS-CoV-2 results in clinical outcomes ranging from silent or benign infection in most individuals to critical pneumonia and death in a few. Genetic studies in patients have established that critical cases can result from inborn errors of TLR3- or TLR7-dependent type I interferon immunity, or from preexisting autoantibodies neutralizing primarily IFN-α and/or IFN-ω. These findings are consistent with virological studies showing that multiple SARS-CoV-2 proteins interfere with pathways of induction of, or response to, type I interferons. They are also congruent with cellular studies and mouse models that found that type I interferons can limit SARS-CoV-2 replication in vitro and in vivo, while their absence or diminution unleashes viral growth. Collectively, these findings point to insufficient type I interferon during the first days of infection as a general mechanism underlying critical COVID-19 pneumonia, with implications for treatment and directions for future research.

Cutaneous coronavirus disease 2019 in children: a clinical primer for diagnosis and treatment

PURPOSE OF REVIEW

This review examines the global literature regarding rashes encountered in children and adults infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and aims to provide practicing pediatricians with an understanding of the relationship between instances of rashes and coronavirus disease 2019 (COVID-19) in children in order to effectively evaluate and treat patients.

RECENT FINDINGS

The true incidence of cutaneous reactions in children infected with SARS-CoV-2 is not known. Children's immune systems differ from those of adults and rashes as a manifestation of immune responses, in turn, differ in morphology and distribution. Rarely, children develop a severe multisystem inflammatory syndrome that has overlapping clinical features with Kawasaki disease. In addition, vaccinations produce rashes similar to natural infections. The rashes associated with COVID-19 vaccination are mild and transient, and should not preclude vaccination. Lastly, children who chronically wear masks are more likely to experience flaring of acne around the nose and mouth ('maskne') and facial conditions such as seborrheic dermatitis.

SUMMARY

There are ongoing worldwide registries, clinical and basic science studies to better understand the burden of skin disease and pathophysiology of rashes seen in patients infected with COVID-19. Robust vaccination programs should be encouraged as a way to contain viral spread among children and the greater population.

Endothelial contribution to COVID-19: an update on mechanisms and therapeutic implications

The global propagation of SARS-CoV-2 leads to an unprecedented public health emergency. Despite that the lungs are the primary organ targeted by COVID-19, systemic endothelial inflammation and dysfunction is observed particularly in patients with severe COVID-19, manifested by elevated endothelial injury markers, endotheliitis, and coagulopathy. Here, we review the clinical characteristics of COVID-19 associated endothelial dysfunction; and the likely pathological mechanisms underlying the disease including direct cell entry or indirect immune overreactions after SARS-CoV-2 infection. In addition, we discuss potential biomarkers that might indicate the disease severity, particularly related to the abnormal development of thrombosis that is a fatal vascular complication of severe COVID-19. Furthermore, we summarize clinical trials targeting the direct and indirect pathological pathways after SARS-CoV-2 infection to prevent or inhibit the virus induced endothelial disorders.

Pathophysiology of infection with SARS-CoV-2-What is known and what remains a mystery

Coronavirus disease 2019 (COVID‐19), caused by coronavirus severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has caused extensive disruption and mortality since its recent emergence. Concomitantly, there has been a race to understand the virus and its pathophysiology. The clinical manifestations of COVID‐19 are manifold and not restricted to the respiratory tract. Extrapulmonary manifestations involving the gastrointestinal tract, hepatobiliary system, cardiovascular and renal systems have been widely reported. However, the pathophysiology of many of these manifestations is controversial with questionable support for direct viral invasion and an abundance of alternative explanations such as pre‐existing medical conditions and critical illness. Prior research on SARS‐Co‐V and NL63 was rapidly leveraged to identify angiotensin‐converting enzyme 2 (ACE2) receptor as the key cell surface receptor for SARS‐CoV‐2. The distribution of ACE2 has been used as a starting point for estimating vulnerability of various tissue types to SARS‐CoV‐2 infection. Sophisticated organoid and animal models have been used to demonstrate such infectivity of extrapulmonary tissues in vitro, but the clinical relevance of these findings remains uncertain. Clinical autopsy studies are typically small and inevitably biased towards patients with severe COVID‐19 and prolonged hospitalization. Technical issues such as delay between time of death and autopsy, use of inappropriate antibodies for paraffin‐embedded tissue sections and misinterpretation of cellular structures as virus particles on electron micrograph images are additional problems encountered in the extant literature. Given that SARS‐CoV‐2 is likely to circulate permanently in human populations, there is no doubt that further work is required to clarify the pathobiology of COVID‐19.