Pre-Mortem Histopathologic Evidence of Endothelial Injury and Thrombotic Microangiopathy in an Infant With...

Area of Science:

• Pediatric Pathology
• Immunology
• Infectious Diseases

Background:

• Multisystem inflammatory syndrome in children (MIS-C) is a severe post-SARS-CoV-2 hyperinflammatory condition.
• Histopathologic data from pre-mortem pediatric biopsies in MIS-C are limited.
• Understanding the early morphologic changes is crucial for diagnosis and treatment.

Purpose of the Study:

• To report histopathologic findings from pre-mortem biopsies in an infant with MIS-C and multiorgan failure.
• To characterize the early vascular and inflammatory changes associated with MIS-C.
• To investigate the role of viral presence versus immune-mediated injury.

Main Methods:

• Analysis of pre-mortem incisional biopsies (myocardium, lung, pleura) from a 9-month-old male infant.
• Histopathologic examination including light microscopy and immunohistochemistry.
• Detection of SARS-CoV-2 antigens via immunohistochemistry.

Main Results:

• Biopsies showed degenerative myocyte changes, endothelial swelling, and microthrombi consistent with thrombotic microangiopathy.
• Immunohistochemistry revealed mild T-cell infiltrates and focal SARS-CoV-2 antigen positivity in respiratory epithelium.
• Myocardial and pleural tissues were negative for SARS-CoV-2 antigens, suggesting limited direct viral involvement.

Conclusions:

• Findings indicate early immune-mediated vascular injury in MIS-C, characterized by endothelial dysfunction and microvascular inflammation.
• The study provides rare pre-mortem evidence of immune-thrombotic endotheliopathy in an infant with MIS-C.
• Pathology is driven by T-cell immunopathology rather than direct viral cytopathy in affected tissues.