EC Pulmonology and Respiratory Medicine

Background: Systemic autoimmune vasculitis (AV) is one of the most important complications of autoimmune diseases, such as rheumatoid arthritis (RA), progressive systemic sclerosis (PSS), polymyalgia rheumatica (PMR), systemic lupus erythematosus (SLE) etc. Autoimmune diseases can be exacerbated by acute bacterial septic infection (AbSI), which is often accompanied by systemic vasculitis of septic origin (SV). Correct diagnosis of AV and SV and early recognition of this serious complication are crucial, due to the fundamental differences in prognosis and in therapy.

Aim of the Study: The aim of the study was to describe the histological features of systemic autoimmune and septic vasculitis so that they can be distinguished from each other histologically, according to the size of affected blood vessels, based on the type of vasculitis and/or by the stages of inflammation (flare ups).

Patients and Methods: Tissue samples of 161 patients with RA, 12 with PSS, and 24 with AbSI were examined post mortem, furthermore surgical samples of 299 patients with PMR. The characteristics of AV in RA, PSS and PMR were compared with those of SV in AbSI.

Results: RA was complicate by AV (with or without rheumatoid nodules) in 33 (20.49%) of 161 patients. AV affected 325 blood vessels in tissue samples of RA patients. PSS was complicate by AV (with or without fibromuscular intimal proliferation - FIP) in 11 (91.67%) of 12 patients (in one patient AV was not assessable because of the massive AL amyloid infiltration of the vessel walls). AV affected 425 blood vessels in tissue samples of PSS patients. PMR was associated with TA in 71 (23.75%) of 299 patients. TA affected 136 blood vessels in tissue samples of PMR patients. RA was complicate by fatal AbSI in 24 (14.98%) of 161 patients. Fatal AbSI was associated with SV in 3 (12.5%) of 24 patients. SV affected 23 blood vessels in tissue samples of fatal AbSI. AV and SV in RA, PSS, PMR and AbSI affected the entire vascular network. AV and SV affected mainly the arterioles and small arteries in RA, PSS, PMR and AbSI patients comparing to the veins; the veins were spared by SV in AbSI. TA affected mainly the medium-sized arteries compared to the arterioles and small arteries or accompanying veins. In RA three types of AV occurred: non-specific, fibrinoid necrotic, and granulomatous vasculitis; granulomatous type was registered only in RA. In PSS and AbSI the AV or SV were characterized by non-specific and occasionally by fibrinoid necrotic vasculitis. In PMR only non-specific vasculitis was registered.

Conclusion: The granulomatous transformation of blood vessels (with or without fibrinoid necrosis) supported the clinical diagnosis of RA, and the autoimmune origin of systemic vasculitis. Rheumatoid nodule was the most severe form of necrotic and/or granulomatous AV, and represented an absolute diagnostic histological sign of RA. In the early stages of PSS, the vascular changes were already present before the connective tissue sclerosis and the characteristic clinical symptoms appeared. Recognizing these changes helps in the early diagnosis of PSS. The fibromuscular intimal proliferation (FIP), with or without fibrinoid necrosis of the blood vessels walls, was an absolute diagnostic histological sign of PSS. Our study confirmed the systemic nature of TA in PMR patients, involving the entire vascular network. The close statistical correlations between inflamed arteries and veins of temporal branches supported that the vasculitis in these vessels are the manifestation of the same disease. SV in RA was less common and less severe than AV in RA. SV was mostly “non-specific,” fibrinoid necrosis occurred, granulomatous transformation of the vessel walls was not detected, and the veins were spared. The absence of granulomatous vasculitis and phlebitis supported the histological diagnosis of SV, i.e. detection of granulomatous vasculitis and phlebitis contradicted the septic origin of systemic vasculitis.

 Keywords: Autoimmune and Septic Vasculitis; Rheumatoid Arthritis; Progressive Systemic Sclerosis; Polymyalgia Rheumatica; Acute Bacterial Septic Infection

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