The "Viral" Form of Polyarteritis Nodosa (PAN)-A Distinct Entity: A Case Based Review

Infection associated Vasculitides

Infections can mimic Primary Systemic Vasculitis. Many clinical features and investigations maybe very similar between the two conditions. It is very important for the clinician to be aware of the various infections which mimic vasculitis, since inadvertent immunosuppression in these patients can be fatal. Infections can mimic small, medium or large vessel vasculitis. Infections can produce autoantibodies such as Anti-neutrophil cytoplasmic antibody through molecular mimicry and could confound clinical judgement. In addition to the many infections causing vasculitis, more recently COVID-19 associated vasculitis has been described. The exact pathogenesis of infection associated vasculitis is not clear although direct spread, immune complex deposition and T/B cell activation are proposed. Infection as an etiological agent for primary systemic vasculitis has long been debated but definite evidence for the same is lacking. Many drugs used in daily clinical practice can rarely cause vasculitis. More recently Immune-check point inhibitors-induced vasculitis has been described.

Polyarteritis Nodosa: Old Disease, New Etiologies

Polyarteritis nodosa (PAN), also known as panarteritis nodosa, represents a form of necrotizing vasculitis that predominantly affects medium-sized vessels, although it is not restricted to them and can also involve smaller vessels. The clinical presentation is heterogeneous and characterized by a significant number of patients exhibiting general symptoms, including asthenia, fever, and unintended weight loss. Although PAN can involve virtually any organ, it preferentially affects the skin, nervous system, and the gastrointestinal tract. Orchitis is a rare but specific manifestation of PAN. The absence of granulomas, glomerulonephritis, and anti-neutrophil cytoplasmic antibodies serves to distinguish PAN from other types of vasculitis. Major complications consist of hemorrhagic and thrombotic events occurring in mesenteric, cardiac, cerebral, and renal systems. Historically, PAN was frequently linked to hepatitis B virus (HBV) infection, but this association has dramatically changed in recent years due to declining HBV prevalence. Current epidemiological research often identifies a connection between PAN and genetic syndromes as well as neoplasia. This article provides a comprehensive review of PAN, specifically focusing on the progression of its clinical manifestations over time.