Multi-Organ System Dysfunction in Covid-19 - A Review

With a continuous increase in Covid-19 cases, patients infected with SARS-CoV-2 have shown a wide variety of symptoms including fever, shortness of breath, cough, myalgia, dizziness, headache, impaired consciousness, abdominal pain and diarrhoea. Lab studies have shown higher leukocyte counts and neutrophil-lymphocyte ratio (NLR), decreased lymphocytes, increased prothrombin time and a partial thromboplastin time, increased serum lactate dehydrogenase, ferritin and various other markers, indicating multiple organ system dysfunction including respiratory system, immune system, nervous system and gastrointestinal tract. Apart from these, heart and kidneys are also found to be affected in some patients. Patients presenting with previous history of diseases such as cardiovascular diseases, kidney diseases, pregnant females, neonates, immunosuppressed patients, and aged people have shown poor prognosis of disease. Various studies suggest possible reasons of multiple organ dysfunctions including wide distribution of angiotensin-converting enzyme 2 (ACE-2) receptors, cytokine storm and hypercoagulability of blood. We have listed the various organ systems affected by the virus and possible explanations as to why and how these organ systems are affected. SARS-CoV-2 outbreak has caused a global pandemic, with more than 33,400,000 confirmed cases of Covid-19, including more than 1,000,000 deaths, reported to World Health Organization (WHO) globally till 30 September 2020.(1) with a basic reproductive number estimated to be 2.2 (1.4 - 3.9) the virus spread is very fast affecting many individuals across the globe.(2) One of the major causes of efficient spread of SARS-CoV-2 in humans is the angiotensin-converting enzyme 2 receptors, used by the virus to enter the cells.(3) Hence, wide distribution of angiotensin-converting enzyme 2 receptors in body including lungs, kidney, bladder, gastrointestinal tract, heart, central nervous system and peripheral nervous system(4) and even placenta(5) is one of the reasons the virus is found to affect these organs. Two closely related viruses causing Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS) were also found to affect multiple organ systems. SARS-CoV-1 was found in the respiratory pathway (trachea, bronchus, lung), gastrointestinal tract (stomach, small intestines), glands (sweat gland, liver, pancreas, parathyroid, pituitary, adrenal gland), renal system (convoluted renal tubules) and brain tissue (cerebrum) in the autopsy samples of patients who died because of severe acute respiratory syndrome.(6) Respiratory, circulatory, gastrointestinal, haematological, renal and hepatological symptoms were also found to be affected in patients with Middle East respiratory syndrome infection.(7) Though the virus is found to affect multiple organ systems, the underlying mechanisms are not clearly understood.