Pain in COVID-19 and features of pathogenetic molecular mechanisms

Although it has been almost three years since the World Health Organization (WHO) declared a pandemic, COVID-19 is still an unsolved problem, thereby attracting great scientific interest. The disease has a heterogeneous clinical picture with multiple manifestations from different organs and systems. Currently, COVID-19 is perceived as a polysyndromic inflammatory disease involving not only the respiratory system, but also the musculoskeletal system, the cardiovascular system, the skin, the excretory and the nervous system, and is accompanied by a number of hematological, gastrohepatoenterological and endocrine disorders. Various pain phenomena also appear in the clinical presentation of the disease, often as a single manifestation or in combination with symptoms from different organs and systems. The pathogenesis of pain is complex and there is still no consensus on the exact driving mechanisms. Several different signaling pathways play an important role in the generation of pain impulses and perception. They are different for different types of pain. At this stage, the role of angiotensin-converting enzyme 2 (ACE), the renin-angiotensin system (RAC), angiotensin 2 receptors (AT2R), direct neuronal invasion of the virus, the involvement of pro-inflammatory cytokines, hypoxia, the involvement of macrophages, is discussed. as well as the role of overactivity of the immune system, causing the so-called "cytokine storm". Pain is the result of complex biochemical processes influenced to varying degrees by biological, physiological and social factors. Our knowledge at this stage remains scarce and is the subject of many studies on the key pathogenic mechanisms. Therefore, the purpose of this review is to describe the known mechanisms for the occurrence and persistence of pain in patients with COVID-19, as well as to classify the pain phenomena and present its most common localizations. The diagnosis and treatment of COVID-19 and associated pain should be carried out by a multidisciplinary team of specialists, given the heterogeneous clinical presentation of the disease.