Retroperitoneal fibrosis encompasses a range of diseases characterised by the presence of a fibro-inflammatory tissue, which usually surrounds the abdominal aorta and the iliac arteries and extends into the retroperitoneum to envelop neighbouring structures--eg, ureters. Retroperitoneal fibrosis is generally idiopathic, but can also be secondary to the use of certain drugs, malignant diseases, infections, and surgery. Idiopathic disease was thought to result from a local inflammatory reaction to antigens in the atherosclerotic plaques of the abdominal aorta, but clinicolaboratory findings--namely, the presence of constitutional symptoms and the high concentrations of acute-phase reactants--and the frequent association of the disease with autoimmune diseases that involve other organs suggest that it might be a manifestation of a systemic autoimmune or inflammatory disease. Steroids are normally used to treat idiopathic retroperitoneal fibrosis, although other options--eg, immunosuppressants, tamoxifen--are available. The outlook is usually good, but, if not appropriately diagnosed or treated, the disease can cause severe complications, such as end-stage renal failure. Here, we review the different aspects of retroperitoneal fibrosis, focusing on idiopathic retroperitoneal fibrosis and on the differential diagnosis associated with the secondary forms.

Objective. Churg-Strauss syndrome (CSS) is classified among the so-called antineutrophil cytoplasmic antibody-associated systemic vasculitides (AASVs) because of its clinicopathologic features that overlap with the other AASVs. However, while antineutrophil cytoplasmic antibodies (ANCAs) are consistently found in 75-95% of patients with Wegener's granulomatosis or microscopic polyangiitis, their prevalence in CSS varies widely and their clinical significance remains uncertain. We undertook this study to examine the prevalence and antigen specificity of ANCAs in a large cohort of patients with CSS. Moreover, we evaluated the relationship between ANCA positivity and clinicopathologic features.Methods. Immunofluorescence and enzymelinked immunosorbent assay were used to determine the presence or absence of ANCAs in 93 consecutive patients at the time of diagnosis. The main clinical and pathologic data, obtained by retrospective analysis, were correlated with ANCA status.Results. ANCAs were present by immunofluorescence in 35 of 93 patients (37.6%). A perinuclear ANCA (pANCA) pattern was found in 26 of 35 patients (74.3%), with specificity for myeloperoxidase (MPO) in 24 patients, while a cytoplasmic ANCA pattern, with specificity for proteinase 3, was found in 3 of 35 patients (8.6%). Atypical patterns were found in 6 of 30 patients with anti-MPO antibodies (20.0%). ANCA positivity was associated with higher prevalences of renal disease (51.4% versus 12.1%; P < 0.001) and pulmonary hemorrhage (20.0% versus 0.0%; P ‫؍‬ 0.001) and, to a lesser extent, with other organ system manifestations (purpura and mononeuritis multiplex), but with lower frequencies of lung disease (34.3% versus 60.3%; P ‫؍‬ 0.019) and heart disease (5.7% versus 22.4%; P ‫؍‬ 0.042).Conclusion. ANCAs are present in ϳ40% of patients with CSS. A pANCA pattern with specificity for MPO is found in most ANCA-positive patients. ANCA positivity is mainly associated with glomerular and alveolar capillaritis.

Eosinophilic granulomatosis with polyangiitis (Churg-Strauss, EGPA) is a systemic small-vessel vasculitis associated with asthma and eosinophilia. Histology of EGPA shows tissue eosinophilia, necrotizing vasculitis, and eosinophil-rich granulomatous inflammation. EGPA commonly presents with upper airway tract and lung involvement, peripheral neuropathy, cardiac and skin lesions. Antineutrophil cytoplasmic antibodies (ANCA) are positive in $ 40% of the cases and more often in patients with clinical manifestations due to small-vessel vasculitis. The pathogenesis of EGPA is multifactorial: the disease can be triggered by exposure to allergens or drugs, but a genetic background has also been recognized, particularly an association with HLA-DRB4. Th2 responses are prominent, with up-regulation of IL-4, IL-13, and IL-5; however, Th1 and Th17 responses are not negligible. Eosinophils are activated, have a prolonged lifespan and probably cause tissue damage by releasing their granule proteins; their tissue recruitment can be regulated by chemokines such as eotaxin-3 and CCL17. Humoral immunity is also dysregulated, as demonstrated by prominent IgG4 and IgE responses. EGPA promptly responds to glucocorticoid therapy, although combinations of glucocorticoids and immunosuppressants (e.g., cyclophosphamide, azathioprine) are eventually required in most cases. Newer therapeutic options include the anti-IL5 antibody mepolizumab, whose efficacy has been described in small clinical trials, and the B-cell-depleting agent rituximab, reported in several case series.In 1951, Churg and Strauss (1) first described a syndrome characterized by asthma and a 'strikingly uniform clinical picture' with 'fever and eosinophilia, and symptoms of cardiac failure, renal damage and peripheral neuropathy resulting from vascular embarrassment in various systems of organs'. Histology of the 13 cases examined by Churg and Strauss (1) was quite similar: in most organs, they found tissue eosinophilia, necrotizing and granulomatous vascular lesions and extravascular granulomas. These features identified a syndrome that could be distinguished from classical polyarteritis nodosa and also by granulomatosis with polyangiitis (Wegener's, GPA). Named Churg-Strauss syndrome for many years, this entity has now been recognized by the 2012 revised nomenclature for vasculitides as eosinophilic granulomatosis with polyangiitis (Churg-Strauss, EGPA) (2).The histological lesions observed by Churg and Strauss in most of the affected sites were extremely severe; it must be considered that most were autopsy cases, and thus, large biopsy specimens were obtained, facilitating detection of the histological hallmarks of EGPA; in addition, glucocorticoid treatment was not available at that time. Glucocorticoids have dramatically changed the prognosis of EGPA; most patients receive glucocorticoids before diagnosis, which may also account for the apparently lower severity of the histopathological lesions we observe today (1, 3).The knowledge on EGPA has recently evolv...

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