COVID-19 is a global pandemic that emerged from Wuhan, China. Besides pneumonia and acute respiratory distress syndrome, the disease leads to multisystem involvement in the form of myocarditis, arrhythmias, cardiac arrest, gastrointestinal symptoms, hypoxemic brain injury, acute liver, and renal function impairment. There are also reports of cutaneous lesions in form of urticarial and maculopapular rashes, chilblain like fingers and toes (covid feet), livedoid vasculopathy, and chicken-pox like or varicelliform vesicles. Clinically, many of these skin lesions are likely secondary to occlusion of small to medium blood vessels due to microthrombi formation or due to viral laden antigen-antibody immune complexes; and same explanation may hold true for possible hypoxemic injury simultaneously occurring in other vital organs like lungs, heart, brain, and kidneys. The histopathology, immunoflorescence and RT-PCR analysis of skin biopsies can provide useful insights for ascertaining the pathogenesis of this complex viral syndrome. Apparently, it is interplay of disarmed cellular immunity and over-activated humoral immunity that culminates in end-organ changes. The morbidity and mortality can be significantly reduced by upgrading the cellular immunity and downgrading the humoral response; along with prevention of hypoxemic and reperfusion injuries by using antivirals, immunomodulators, antioxidants, antiplatelets, and anticoagulants in judicious and phased manner.

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Dept. of Radiodiagnosis and ImagingPGIMER. Chandigarh. Sector-12 "In Press" papers have undergone full peer review and have been accepted for publication in Radiology. This article will undergo copyediting, layout, and proof review before it is published in its final version. Please note that during production of the final copyedited article, errors may be discovered which could affect the content.

Chest radiography is generally the first imaging modality used for the evaluation of pneumonia. It can establish the presence of pneumonia, determine its extent and location, and assess the response to treatment. Computed tomography is not used for the initial evaluation of pneumonia, but it may be used when the response to treatment is unusually slow. It helps to identify complications, detect any underlying chronic pulmonary disease, and also to characterise complex pneumonias. Although not diagnostic, certain imaging findings may suggest a particular microbial cause over others. Knowledge of whether pneumonia is community-acquired or nosocomial, as well as the age and immune status of the patient, can help us in narrowing the differential diagnoses. The purpose of this article is to briefly review the various pulmonary imaging manifestations of pathogenic organisms. This knowledge along with clinical history and laboratory investigations of the patient may help in guiding the treatment of pneumonia.

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