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Proliferative lupus nephritis (LN) progresses to end-stage kidney disease (ESKD) in roughly 10% of the cases despite treatment. Other than achieving 0.8 g/24h proteinuria at 12 months after treatment, early biomarkers predicting ESKD or death are lacking. Recent studies encompassing not only LN have highlighted the central role of the alternative complement pathway (ACP), with or without histological evidence of thrombotic microangiopathy (TMA), as a key promotor of renal death.We assessed whether persistent isolated C3 hypocomplementemia (PI-LowC3), that is not accompanied by C4 hypocomplementemia, 6 months after kidney biopsy, is associated with an increased risk of death or ESKD in proliferative LN.We retrospectively followed-up 197 patients with proliferative LN (51 with PI-LowC3) for a median of 4.5 years (interquartile-range: 1.9-9.0), 11 of whom died and 22 reached ESKD. After adjusting for age, gender, ethnicity, hypertension, mycophenolate, or cyclophosphamide use, PI-LowC3 was associated with a hazard ratio [HR] of the composite outcome ESKD or death of 2.46 (95% confidence interval [CI]: 1.22-4.99,Our findings support the use of PI-LowC3 as a low-cost readily available biomarker, allowing clinicians to modify treatment strategies early in the course of disease and offering a rationale for complement blockade trials in this particularly at-risk subgroup of LN patients.

Introduction In patients with systemic lupus erythematosus (SLE) without concurrent active urinary sediment or unexplained acute kidney injury (AKI), current guidelines recommend performing a kidney biopsy in those with at least 500 mg/24-hour (European League Against Rheumatism/European Renal Association-European Dialysis and Transplant Association [EULAR/ERA-EDTA]) or 1000 mg/24-hour (American College of Rheumatology [ACR]) proteinuria. To evaluate the relevance of these indications, we studied histopathologic findings in patients with SLE with proteinuria below these cutoffs. Methods We retrospectively reviewed the clinical, laboratory and histological characteristics of patients with SLE with, Graphical abstract

OBJECTIVE Eosinophilic granulomatosis with polyangiitis (EGPA) is a rare antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Environmental agents and occupational exposures may confer susceptibility to EGPA, but data are scarce. This study was undertaken to investigate the association between occupational exposures (e.g., silica, farming, asbestos, and organic solvents) and other environmental agents (e.g., smoking) and the risk of EGPA. METHODS Patients with newly diagnosed EGPA (n = 111) and general population controls (n = 333) who were matched for age, sex, and geographic area of origin were recruited at a national referral center for EGPA. Exposures were assessed using a dedicated questionnaire administered by a specialist in occupational medicine, under blinded conditions. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated. RESULTS Exposures to silica (OR 2.79 [95% CI 1.55-5.01], P = 0.001), organic solvents (OR 3.19 [95% CI 1.91-5.34], P < 0.001), and farming (OR 2.71 [95% CI 1.71-4.29], P < 0.001) were associated with an increased risk of EGPA. Co-exposure to silica and farming yielded an OR of 9.12 (95% CI 3.06-27.19, P < 0.001), suggesting a multiplicative effect between these 2 exposures. Smoking (current and former smokers combined) was significantly less frequent among patients with EGPA compared to controls (OR 0.49 [95% CI 0.29-0.70], P < 0.001). The pack-year index was also lower among patients with EGPA (OR 0.96 [95% CI 0.94-0.98], P < 0.001). The association of silica and farming was primarily aligned with ANCA-positive EGPA, while the association of smoking status and organic solvents was primarily aligned with ANCA-negative EGPA. CONCLUSION The environment can influence susceptibility to EGPA. Exposure to silica, farming, or organic solvents is associated with an increased risk of EGPA, while smoking is associated with a lower risk. These exposures seem to have distinct effects on different EGPA subsets.

IntroductionIn patients on maintenance haemodialysis (HD), intradialytic hypotension (IDH) is a clinical problem that nephrologists and dialysis nurses face daily in their clinical routine. Despite the technological advances in the field of HD, the incidence of hypotensive events occurring during a standard dialytic treatment is still very high. Frequently recurring hypotensive episodes during HD sessions expose patients not only to severe immediate complications but also to a higher mortality risk in the medium term. Various strategies aimed at preventing IDH are currently available, but there is lack of conclusive data on more integrated approaches combining different interventions.Methods and analysisThis is a prospective, randomised, open-label, crossover trial (each subject will be used as his/her own control) that will be performed in two distinct phases, each of which is divided into several subphases. In the first phase, 27 HD sessions for each patient will be used, and will be aimed at the validation of a new ultrafiltration (UF) profile, designed with an ascending/descending shape, and a standard dialysate sodium concentration. In the second phase, 33 HD sessions for each patient will be used and will be aimed at evaluating the combination of different UF and sodium profiling strategies through individualised dialysate sodium concentration.Ethics and disseminationThe trial protocol has been reviewed and approved by the local Institutional Ethics Committee (Comitato Etico AVEN, prot. 43391 22.10.19). The results of the trial will be presented at local and international conferences and submitted for publication to a peer-reviewed journal.Trial registration numberClinicalTrials.gov Registry (NCT03949088).

Background and Aims Despite the obvious efficacy in achieving weight loss, traditional malabsorptive procedures (intestinal by-pass) used for the treatment of obesity, may be associated with enteric oxaluria. Enteric oxaluria, by causing calcium-oxalate stones and nephrocalcinosis, represents an under-recognized cause of end-stage kidney disease in patients with history of intestinal by-pass. Herein, we describe a patient with a long-standing history of intestinal by-pass who developed a devastating acute oxalate nephropathy first diagnosed after kidney transplantation. Method A white female aged 50, who started hemodialysis one year earlier because of tubule-interstitial nephritis on a kidney biopsy, and who had history of recurrent kidney stones (calcium oxalate), underwent urgent deceased-donor kidney transplantation because of exhausted vascular access for hemodialysis (tunneled CVC right giugular vein as the last resort). She had received intestinal by-pass surgery 20 yrs earlier, and had a pacemaker implantation in the left sublavian vein for AV block two years earlier. She was highly sensitized because of blood transfusions at the time of surgery. Results After transplantation, graft function had immediate recovery, serum creatinine decreasing to 2.0mg/dL (117 mmol/L) on post-operative day (POD) 3. Shortly after, serum creatinine started rising until it reached 4.0mg/dL (354mmol/L) on POD 5. Three graft biopsies (performed on POD 6, 9 and 15 post-transplant) revealed acute oxalate nephropathy ( Figure1-2 large oxalate crystals on fresh unfixed core of kidney tissue analyzed under bright field microscope using polarized light) with no sign of rejection. Serial monitoring of Luminex SAB did not reveal circulating anti-HLA donor specific antibodies. Fundus examination revealed two tiny mono-lateral retinal oxalate deposits, whereas bone biopsy did not reveal oxalate accumulation. Plasma oxalate levels were 43 mmol/L on POD 10 were urinary oxalate excretion was 29mg /day on POD 14. The patient slowly progressed to end-stage kidney disease 2-month post-transplantation despite daily high flux dialysis since POD 7, fat-free and oxalate-free diet, oral potassium and high dose pyridoxine supplements. Conclusion Patients on chronic dialysis with a previous history of bariatric surgery via intestinal by-pass may have oxalate nephropathy caused by enteric oxaluria as unknown primary renal disease. The disease may recur shortly after transplantation despite the adoption of prompt aggressive treatment for oxalate removal.

Background and Aims Eosinophilic granulomatosis with polyangiitis (EGPA, formerly Churg-Strauss Syndrome) is a rare systemic disease, included in the group of antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV), characterized by adult-onset asthma, blood and tissue eosinophilia with organ involvement, and small-vessel vasculitis. The pathogenesis of the disease is poorly understood, but it is likely that immunogenetic factors play a crucial role in its development. However, it has been suspected that the disease may be triggered by exogenous factors including environmental agents, infections, vaccinations, and drugs. Data about the association between individual, environmental and occupational risk factors and the development of EGPA are scarce. In this study we aimed to investigate the role of occupational agents (such as silica, farming, organic solvents and chemical agents) as well as individual agents (such as smoking habits) and their interactions, as potential risk factors for EGPA. Method The study has a case-control design. We enrolled 111 patients with EGPA and 333 healthy controls, matched for age, sex and geographical origin. Occupational history was obtained using a structured questionnaire administered by blinded specialists in occupational medicine. The exposures to non-occupational risk factors potentially predisposing to EGPA were assessed through the interview and through the examination of medical records. All exposures were considered until the time of EGPA diagnosis. Results At a multivariate logistic regression analysis, EGPA was associated with silica exposure (OR 2.26 [95% CI 1.10-4.62], p=0.026), farming (OR 2.10 [95% CI 1.19-3.73], p=0.011) and with the exposure to organic solvents (OR 2.20 [95% CI 1.14-4.2], p=0.018). There was a positive relationship between the duration of exposure to silica, chemical agents and the risk of developing EGPA (Figure 1). A multiplicative effect on risk was found for the co-exposure of silica and farming (OR 7.49 [95% CI 2.77-20.25], p Conclusion This is, to our knowledge, the first study investigating the role of environmental, occupational and individual risk factors in the development of EGPA, through the comparison of a group of EGPA patients with a group of healthy controls, matched for age, gender and geographical origin. Our results demonstrate that occupational factors may significantly contribute to the development of the disease. In particular, we found a significative association between exposure to silica, farming, organic solvents and EGPA. In addition, our findings reveal that tobacco smoking has a protective role against the disease. Further studies are necessary to investigate the biological effects of such risk factors on disease pathogenesis.

Background and Aims Sustained-Low Efficiency Dialysis (SLED) is a hybrid Renal Replacement Therapy (RRT) increasingly used in critically ill patients with Acute Kidney Injury (AKI). Usually lasting 8-12 hours, this modality combines several advantages of both intermittent and continuous RRT (CRRT). Regional citrate anticoagulation (RCA) represents the most adequate anticoagulation strategy to avoid the extracorporeal circuit clotting. Hypophosphatemia (serum phosphorus, s-P, levels ≤ 2.5 mg/dl) is a common electrolyte disorder in critically ills, with an increased incidence in course of prolonged RRTs, especially when standard dialysis/replacement solutions and highly intensive modalities are employed. Given the potentially negative impact of hypophosphatemia on patients’ outcomes, strategies aimed at preventing its onset should be appropriately implemented. This pilot study is aimed at evaluation of safety and efficacy of a simplified RCA protocol for SLED, based on the combination of a low-concentrated citrate solution with a phosphate-containing solution. Methods a prospective observational study was conducted on critically ill patients with AKI requiring RRT or End Stage Renal Disease (ESRD) previously on RRT admitted to our renal Intensive Care Unit (ICU). SLED was performed by the Prismax system (Baxter) and polyacrylonitrile AN69 haemofilters (ST 150, 1.5 m2, Baxter). 8-hours SLED sessions were prescribed, in the SLED-f variant, by using a 18 mmol/l pre-dilution trisodium citrate solution (Regiocit 18/0, Baxter) combined with a phosphate-containing solution acting as dialysate (Ca2+ 0, HPO42- 1, Mg2+ 0.75, HCO3- 22 mmol/l; Biphozyl, Baxter) and a standard RRT solution acting as post-dilution replacement fluid (Prismasol 4, Baxter). Calcium chloride (CaCl 10%) was infused in a separate central venous line to maintain the systemic Ca2+ (s-Ca2+) within a normal range. Each patient underwent three consecutive daily SLED sessions. The activated coagulation time (ACT), acid–base parameters, s-Ca2+ and potassium were measured at SLED start and every 2 h. Phosphorus and magnesium losses with RRT were replaced, when needed, with sodium glycerophosphate pentahydrate (GlycophosTM 20 mmol/20 ml, Fresenius Kabi Norge AS, Halden, Norvegia) and magnesium sulphate. Results a total of 60 SLED-f sessions were performed in 20 ICU patients. At ICU admission, the average APACHE II score was 21.8 and half of patients were mechanically ventilated. Many of them showed hemodynamic instability and AKI was oliguric in 90% of cases. No premature interruptions for irreversible filter clotting occurred and the prescribed dialysis dose was delivered in 95% of cases. No statistically significant differences were observed between systemic ACT at SLED start and during RRT sessions, and no major hemorrhagic events were observed. Regarding RCA, no clinically relevant episode of hypo or hypercalcemia was observed, and calcium infusion rate remained constant in course of treatments. Acid-base status was effectively maintained during the entire period of treatment and no episodes of clinically relevant metabolic acidosis or alkalosis were registered. The analysis of the main laboratory variables at SLED start, in course and after 24 h of treatment did not show statistically significant differences. Regardless of starting values, s-P and s-Mg were progressively corrected and maintained within the normality range, limiting the need for exogenous supplementations. Conclusions These preliminary data suggest that our simplified RCA protocol for SLED, combining a low-citrate solution with a phosphate-containing solution, is safe and efficacious allowing to optimizing acid-base balance and to preventing RRT-related hypophosphatemia.

Background and Aims ADPKD is characterized by the progressive development of bulky renal cysts, often resulting in end-stage renal disease (ESRD). Among this group 85% of cases recognize a genetic mutation concerning PKD1/PKD2 genes (ADPKD). Among the remaining 15% of ADPKD patients, DNAJB11 mutations (DNAJB11-PKD) has been recently recognized. [Cornec-Le Gall E, Olson RJ, Beesse W t al. Monoallelic Mutations to DNAJB11 Cause Atypical Autosomal-Dominant Polycystic Kidney Disease. Am Journ Hum Gen 2018, 102:832-844.] DNAJB11 encodes a co-chaperone of the endoplasmic reticulum (ER) also called ERdj3. It is part of the HSP40 protein family and plays a central role in both intracellular and extracellular proteomic homeostasis (proteostasis). In the intracellular compartment it acts as a co-chaperone in the pathway of the unfolded protein response (UPR) in which it binds misfolded proteins which have to be secreted and activates BiP an HSP70 of ER whose function is to correct the misfolding. In our Nephrology Unit we collected the largest cohort of patients with a new stop codon mutation (p.Arg34*) of DNAJB11. All patients are relatives of different ranks and were born in a small village in the mountains of the Parma province.In this study we compare clinical features of DNAJB11-PKD with ADPKD to define differences between the two groups. Method We identified retrospectively from outpatient and dialysis databases of the Nephrology Unit of Parma patients carrying pArg34* DNAJB11 or PKD1-PKD2 mutations. We collected the clinical features and the available diagnostic imaging of all identified patients. Results We collected 19 patients with DNAJB11-PKD and 37 with ADPKD. The clinical characteristics are reported in Figure 1 . Our DNAJB11-PKD cohort vs ADPKD presented significantly a normal renal size (median value 10.5cm vs 16cm respectively) and smaller cysts size (median value 2cm vs 5cm respectively). Interestingly 5/19 DNAJB11 patients had type 2 diabetes vs no cases in the ADPKD group (p Conclusion DNAJB11 mutations were reported as a cause of ADPKD for the first time in May 2018 by Cornec-Le-Gall and colleagues. In their study were reported 7 different mutations in 23 patients and they identified 2/23 patients with type II diabetes. We here report the larger single DNAJB11 mutation cohort in the literature and compared it with genetic proven ADPKD. We documented differences in pathognomonic clinical features of ADPKD like renal survival, enlarged kidneys and bulky cysts. Moreover about 30% of DNAJB11-PKD patients present Type II diabetes that would be related to altered proteostasis in the ER. Since DNAJB11-PKD appears to differ in relevant aspects from well known ADPKD, it would be less confusing to classify DNAJB11-PKD indipendently from ADPKD.

Background and Aims The prognosis of lupus nephritis (LN) has become progressively more favorable thanks to the introduction of cyclophosphamide and mycophenolate as the mainstay of induction of remission treatment regimens. However, 10-15% of patients still progress to end-stage renal disease (ESRD). Early predictors of ESRD, i.e. in the first six months between kidney biopsy and the completion of induction, are currently limited to few histological and clinical features: ≥ 25% interstitial fibrosis and tubular atrophy (IFTA), fibrinoid necrosis, fibrous crescents, and thrombotic microangiopathy (TMA) [Rijnink EC et al CJASN 2017; Song D Arthritis Res Ther 2013]; lack of decrease in proteinuria < 0.5 g/24-h at 3 and 6 months from kidney biopsy [Tamirou F Ann Rheum Dis 2016], baseline GFR ≤ 90 ml/min/1.73 m2, lack of decrease in urinary protein-to-creatinine ratio (UPCR) < 1 and anti-dsDNA positivity at the end of induction [Dall’Era M Lupus Sci Med 2015]. In this study we sought to identify further clinical and histological predictors of ESRD in LN. Methods Adult patients diagnosed with LN between 1995 and 2018 in two centers (NIAMS, Bethesda, Maryland, USA, and Nefrologia, AOU di Parma, Italy) were retrospectively identified. Patients with available serum C3 and C4 levels at the time of biopsy and 6 months thereafter, and a follow-up of at least 6 months, were included. Baseline and follow-up data (until March 2019) including age, sex, ethnicity, clinical, histological and laboratory findings were collected. Histology slides were reviewed by an experienced renal pathologist and biopsies re-scored using the ISN/RPS classification and NIH activity and chronicity indices. Distinct histological features were assessed individually (e.g. TMA). Persistent C3 hypocomplementemia was defined as decreased serum C3 levels at the time of biopsy and after 6 months (i.e. after the completion of induction), with concurrent normal serum C4 levels at 6 months. Early renal recovery was defined as either an increase in eGFR above 60 in those with a baseline eGFR < 60 ml/min/1.73 m2, or a 50% decrease in proteinuria in those with a baseline eGFR ≥ 60 ml/min/1.73 m2 and ≥ 0.5 g/24-h or g/g UPCR at the time of biopsy. Variables were tested for their predictive power of death-censored ESRD in univariate and multivariate Cox regression models. Results 74 patients (NIAMS n = 36; Parma n = 38) met our criteria. Median follow-up duration was 64 months (range 6-230). On univariate analysis, the following parameters predicted ESRD: Hispanic ethnicity; age at biopsy; persistent C3 hypocomplementemia; normalization of both C3 and C4; renal recovery after induction; NIH activity index; presence of TMA; ≥ 25% IFTA. Multivariate Cox regression models for ESRD were created considering statistically significant variables (p < 0.05). In a model including Hispanic ethnicity, age at biopsy, and persistent C3 hypocomplementemia, the latter predicted ESRD with an HR of 5.22 (95% CI [1.33, 20.58] p = 0.018) when adjusting for renal recovery after induction. Upon including histological features in the model, persistent C3 hypocomplementemia, TMA, and the NIH activity index lost significance, while ≥ 25% IFTA predicted ESRD with an HR of 27.26 (95% CI [2.12, 350.54], p = 0.011). Conclusion In patients with LN, ≥ 25% IFTA at baseline biopsy is a predictor of ESRD, allowing for early risk stratification with the potential of informing treatment strategies. Where percent IFTA is unavailable or its assessment unreliable (e.g. inadequate biopsy specimen for tubulointerstitial assessment), persistent C3 hypocomplementemia represents a reliable and reproducible early predictor of ESRD, irrespective of early renal recovery after induction.

Two articles this week focus on Erdheim-Chester disease (ECD), a rare histiocytosis that mainly affects adults. Clonal somatic mutations primarily involving proteins in the BRAF and MPAK pathways have established ECD as a myeloid neoplasm, with targeted therapies now available for patients. In the first paper, an international panel presents new consensus recommendations for evaluation and treatment of ECD. In the second paper, Pegoraro and colleagues present long-term outcomes of patients with ECD treated with sirolimus, with responses in patients both with and without BRAF mutations.

Chronic periaortitis (CP) is a rare condition characterised by a peri-aortoiliac fibro-inflammatory tissue. A total of 20%–50% of the cases are immunoglobulin G4 (IgG4)-related, based on histological evidence of IgG4+ plasma cell infiltration (on a background of dense lymphoplasmacytic infiltrates, storiform fibrosis and tissue eosinophilia) and/or increased serum IgG4.1 Glucocorticoids are the first-line therapy for CP.2 However, some patients are refractory, frequently relapsing or have contraindications to glucocorticoids. The anti-CD20 monoclonal antibody rituximab proved efficacious in systemic forms of IgG4-related disease (IgG4-RD) including IgG4-related CP,3 but data on IgG4-unrelated CP are scarce.4–6 In this study, we tested rituximab in CP patients without evidence of IgG4-RD who had relapsing/refractory disease or contraindications to standard-dose glucocorticoids. We included patients with active, IgG4-unrelated CP who received rituximab (October 2009 to April 2017). Online supplementary methods describe the diagnostic and follow-up procedures, the definitions of remission and refractory, and the statistical analysis.### Supplementary data [annrheumdis-2019-216258supp001.pdf] Twenty consecutive patients were included. Two of them were previously reported.5 Of the eight patients with available CP biopsies, none had significant IgG4+-plasma cell infiltration. None had other biopsy-proven …

IgG4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory disorder that can affect almost any organ. Common presentations include major salivary and lacrimal gland enlargement, orbital disease, autoimmune pancreatitis, retroperitoneal fibrosis and tubulointerstitial nephritis. The main histopathological features are a dense, polyclonal, lymphoplasmacytic infiltrate rich in IgG4+ plasma cells, storiform fibrosis and obliterative phlebitis. The precise pathogenic mechanisms of IgG4-RD are still unclear. CD4+ T and B cells, including IgG4-expressing plasmablasts, constitute the major inflammatory cell populations and are believed to cause organ damage and tissue fibrosis. The diagnosis of the disease may be challenging and should be based on specific histopathological findings, typical laboratory and radiological aspects and an appropriate clinical context. The first-line treatment of IgG4-RD is based on glucocorticoids, which are usually efficacious. However, B cell depletion induced by rituximab has also been found to induce remission in steroid-resistant disease or has been used as steroid-sparing agent for relapsing disease. This review provides an update on clinical and therapeutic aspects of IgG4-RD.

As our understanding of the physiology of the aldosterone-sensitive distal nephron (ASDN) advanced in light of novel acquisitions, mainly pertaining the regulation of key ion channels and transporters by with-no-lysine kinases, the pathophysiology of a variety of conditions affecting this segment of the nephron was partly or fully elucidated as well. The pathophysiology of tubulopathies affecting the ASDN or strictly related nephron segments, and disorders causing aldosteronism, pseudoaldosteronism and pseudohypoaldosteronism are here reviewed. The clinical features, with a strong emphasis on pathophysiology, of a variety of disorders are discussed, including: Liddle, Gordon (and calcineurin inhibitor-related hypertension), and Geller syndrome; apparent mineralocorticoid excess; Bartter and Gitelman syndromes; primary aldosteronism, including familial forms; generalized glucocorticoid resistance (Chrousos syndrome). Moreover, the pharmacological translational potential of such novel acquisitions is briefly discussed.

In recent years, our understanding of the physiology of the aldosterone-sensitive distal nephron (ASDN) has greatly advanced thanks to the discovery of the complex with-no-lysine kinase (WNK) signaling and the molecular characterization of the epithelial sodium channel (ENaC). A series of studies, initially focused on rare tubulopathies such as Gordon and Liddle syndromes, eventually led to a partial elucidation of the so-called "aldosterone paradox", the traditional explanation of the physiology of such disparate conditions such as hyperkalemia and low effective arterial blood volume. The physiology of the ASDN is herein illustrated in light of the novel acquisitions in an easy-to-understand fashion, with the aim of giving the practicing nephrologist a solid "first glance" into this exciting but challenging field. Focus is on ion channels and transporters, their regulation by key hormones such as aldosterone and angiotensin II, and dietary implications.

Accelerated muscle wasting still represents a major issue in critically ill patients. However, a key problem in the intensive care unit is the lack of adequate tools for bedside evaluation of muscle mass. Moreover, when acute kidney injury (AKI) coexists, fluid overload and/or rapid fluid shifts due to renal replacement therapies that frequently occur and may interfere with muscle mass assessment. The purpose of this study is to validate muscle ultrasound (US) by a gold standard (muscle CT scan) for the assessment of quadriceps muscle thickness in critically ill patients with AKI. Quadriceps rectus femoris thickness and quadriceps vastus intermedius thickness of critically ill patients with AKI were blindly assessed at the same leg sites by both US and computed tomography (CT) scan. Using bivariate mixed-model linear regression analysis, we estimated, average difference in thickness between measurement sites, agreement (differential and proportional bias) of US compared to CT, and precision of the two methods, and eventually performed Bland–Altman analysis for repeated measurements on pooled results. We analyzed 233 couples of measurements (30 patients). Average muscle thickness ranged between 1.0 and 1.6, depending on the measurement site. When comparing US to CT, both the observed differential bias (between + 0.04 and + 0.26 cm depending on the muscle site) and the proportional bias (between 82 and 98% of the reference values, depending on the muscle site) were not statistically significant. However, precision analysis showed that US scan tended to be slightly less precise in comparison to CT. Bland–Altman analysis on pooled results showed that the 95% limits of agreement between the US and CT were narrow, ranging from − 0.34 to + 0.36 cm. In critically ill patients with AKI, quadriceps muscle thickness assessment based on US is unbiased, although it occurs with a minor loss of precision compared to CT.

Objective: Chronic periaortitis (CP) is a rare fibro-inflammatory disorder that incorporates idiopathic retroperitoneal fibrosis, inflammatory abdominal aortic aneurysms, and perianeurysmal retroperitoneal fibrosis. CP is included in the spectrum of IgG4-related disease. Since CP patients rarely undergo diagnostic biopsies, serum IgG4 levels are often used to classify CP as IgG4-related. However, the clinical and prognostic significance of serum IgG4 in CP is unknown. Methods: We measured serum IgG4 in active CP patients and compared the clinical characteristics, response to therapy and outcome of patients with high and normal levels. We also tested the diagnostic significance of IgG4 by comparing its levels in CP patients, healthy and disease controls (malignancies, Erdheim-Chester disease, large-, and small-vessel vasculitis). Results: We studied 113 consecutive patients with active CP. Twenty-four (21.2%) had high serum IgG4 (>135 mg/dL). The demographic, laboratory, and clinical characteristics of patients with high and normal IgG4 were similar, and so were the rates of ureteral obstruction and the disease characteristics on CT, MRI, and 18F-FDG-PET. Patients with high IgG4 only had a higher frequency of extra-retroperitoneal fibro-inflammatory lesions (p = 0.005). There were no significant differences in response to therapy and relapses between the two groups. Serum IgG4 levels did not discriminate CP from controls. Conclusions: Serum IgG4 levels are high in a minority of CP patients and do not identify specific clinical or prognostic subgroups; only a higher frequency of extra-retroperitoneal lesions is found in high-IgG4 patients. Serum IgG4 levels do not help in the differential diagnosis between CP and its mimics.

Objective Chronic periaortitis (CP) is a rare disease characterized by periaortic and periiliac fibroinflammatory tissue. The pathogenic mechanisms leading to tissue accumulation and activation of fibroblasts are unclear. This study was undertaken to explore the role of fibrocytes, circulating precursors of tissue fibroblasts, in patients with CP. Methods We studied 44 patients with newly diagnosed CP and 30 healthy controls. Circulating fibrocytes were identified as Col1+CD45+ cells using flow cytometry. Retroperitoneal tissue biopsy samples from 9 CP patients were stained with anti-type I procollagen, anti-CXCR4, and anti-CD45 antibodies and analyzed by confocal microscopy to detect tissue-infiltrating fibrocytes. Circulating levels and tissue expression of CXCL12, a CXCR4 ligand that promotes fibrocyte homing, were investigated using enzyme-linked immunosorbent assay and immunohistochemistry, respectively. We also characterized T helper polarization in biopsy samples from CP patients and measured serum levels of a panel of cytokines that are hallmarks of T helper responses and capable of influencing fibrocyte differentiation. Results The frequency of circulating Col1+CD45+ fibrocytes was higher in patients than in controls (P = 0.0371). CD45+proCol1+ and CXCR4+proCol1+ cells were detected in all examined biopsy samples from CP patients. Serum levels of CXCL12 were also higher in CP patients than controls (P = 0.0056), and tissue-infiltrating inflammatory cells intensely expressed CXCL12. Increased serum levels of Th2 cytokines (e.g., interleukin-13 [IL-13] and IL-10) were found in patients, and immunohistochemistry revealed a dominant infiltration of GATA-3+ cells, also indicating Th2 polarization; Th2-skewed responses are known to promote fibrocyte differentiation. Conclusion Our findings indicate that fibrocytes are enriched in the peripheral blood of CP patients and infiltrate target lesions. The accumulation of fibrocytes in the pathologic tissue might be driven by CXCL12, and Th2-skewed immune responses are likely to facilitate their differentiation.