Necrotizing Raynaud's phenomenon after recurrent COVID-19 infection

Raynaud's phenomenon (RP), which can be primary or secondary, is a common vascular clinical syndrome due to abnormal arteriolar vasospasm. Its treatment is most often conservative depending on the etiology. In recent years, there have been reports of RP as a syndrome after a previous SARS-CoV-2 infection, in patients of different genders and ages. As an etiological factor for the development of vascular pathology in these cases, two main mechanisms are assumed: an autoimmune process or the thrombosis of arterial vessels, leading to tissue ischemia, and the so-called necrotizing Raynaud's phenomenon. In the pathogenesis of Raynaud's phenomenon, the influence of local, neuronal and hormonal mediators is emphasized. Some studies prove the role of estrogens, which explains the higher incidence of RP among women. At present, there is no convincing evidence for "candidate genes" to be associated with Raynaud's phenomenon, despite studies by some authors (Susol et al., 2000; Pistorius et al., 2006). Vasospasm in digital ischemia may be further complicated by COVID-19 infection. Another potential component is hypercoagulation (further complicated by the presence of antiphospholipid antibodies in certain patients) and elevated levels of D-dimer. A state of hypercoagulation is caused by the so-called cytokine storm. This inflammatory state, as a result of endovascular damage, increased platelet activity and coagulation cascade, causes the so-called phenomenon of immunothrombosis. Overactivation of the coagulation pathway during cytokine storm results from increased activity of thrombin, which has an additional role in the inflammatory process through proteinase-activated receptors (PARs). Acrocyanosis due to excessive coagulation status has been described in critically ill patients with COVID-19. In these patients, gangrene may arise from impaired blood flow and insufficient healing of digital wounds, which is associated with elevated levels of C-reactive protein (CRP). Ischemic limb lesions, usually seen in older patients with severe clinical course of the disease, represent a dangerous, although rare, complication associated with COVID-19 and are due to arterial occlusions. They are extremely difficult to treat and often lead to amputations. In patients with antiphospholipid syndrome, arterial and venous thrombi are primarily caused by the formation of neutrophil extracellular traps (NET), which in turn activate platelets, and their excessive formation can lead to local thrombosis. In addition to platelet activation, neutrophils release tissue factor, which initiates the coagulation cascade. NETs bind coagulation factor XII and activate it, and also induce an inflammatory reaction in the vessel wall. According to the available knowledge to date, the hypothesis that digital necrosis in patients with COVID-19 is primarily related to the formation of NETs has been developed. Necrotizing Raynaud's phenomenon (NRP) is a vascular clinical syndrome characterized by vasoconstriction of distal resistance vessels following low temperatures or states of anxiety and stress. The first symptom is pain, due to lack of oxygen, which leads to tissue ischemia. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can cause endotheliopathy with microvascular and macrovascular thrombotic events. COVID-19 induces hypercoagulation, thrombosis, endothelial damage, and inflammation leading to vasculitis. The coagulopathy, inflammation, and thrombosis seen in COVID-19 are potentiated by increased activity of clotting factors, loss of protective glycocalyx function, and decreased nitric oxide levels. The effects of COVID-19 in patients with RP are still being elucidated. This review presents a series of selected clinical cases associated with Raynaud's phenomenon (necrotic, new-onset, exacerbated, or as part of another systemic connective tissue disease) secondary to past COVID-19 infection or vaccination.