Borczuk Alain C
Weill Cornell Medicine, Department of Pathology and Laboratory Medicine, New York, New York, USA.
Curr Opin Pulm Med. 2021 May 1;27(3):184-192. doi: 10.1097/MCP.0000000000000761.
COVID-19 lung injury is a common manifestation of severe illness. Lung tissue examination has been largely derived from autopsy - a combination of case reports, small and moderately sized series with international scope. Common and uncommon histopathology provides insight into the progression of severe, fatal disease.
COVID-19 lung histology is most commonly diffuse alveolar damage as part of acute respiratory distress syndrome. Lung injury can be temporally heterogeneous, with patterns of healing alongside new injury. Viral studies, including immunohistochemistry, RNA in-situ hybridization, and tissue-based Polymerase chain reaction (PCR) assist in discerning complications of therapy (e.g. ventilator-associated pneumonia) from primary viral-induced injury. Response to viral infection produces systemic effects, and one major manifestation is thrombosis of micro-circulation and larger vessels. Less common patterns include neutrophil-rich inflammation, raising speculation that neutrophil extra-cellular traps may play a role in both viral control and exaggerated immune response.
The heterogeneity of fatal cases- persistence of viral infection in lung, clearance of virus but severe lung injury, thrombosis, and exaggerated immune response - suggest that antiviral, antithrombotic, anti-inflammatory, and supportive therapy play a role in treatment, but that the patient-specific cause and timing of the lung injury is important in choosing intervention.
新型冠状病毒肺炎（COVID-19）肺损伤是重症患者的常见表现。肺组织检查主要来源于尸检——包括病例报告、具有国际范围的小型和中型系列研究。常见和不常见的组织病理学有助于深入了解严重致命疾病的进展情况。
COVID-19肺部组织学最常见的是作为急性呼吸窘迫综合征一部分的弥漫性肺泡损伤。肺损伤在时间上可能是异质性的，存在愈合模式与新损伤并存的情况。病毒学研究，包括免疫组织化学、RNA原位杂交和基于组织的聚合酶链反应（PCR），有助于区分治疗并发症（如呼吸机相关性肺炎）与原发性病毒诱导的损伤。对病毒感染的反应会产生全身影响，一个主要表现是微循环和较大血管的血栓形成。不太常见的模式包括富含中性粒细胞的炎症，这引发了中性粒细胞胞外陷阱可能在病毒控制和过度免疫反应中都起作用的推测。
致命病例的异质性——病毒在肺内持续存在、病毒清除但肺损伤严重、血栓形成和过度免疫反应——表明抗病毒、抗血栓、抗炎和支持性治疗在治疗中发挥作用，但在选择干预措施时，患者特异性的肺损伤原因和时间很重要。
