Developments in the Histopathological Classification of ANCA-Associated Glomerulonephritis.

BACKGROUND AND OBJECTIVES: The histopathologic classification for ANCA-associated GN distinguishes four classes on the basis of patterns of injury. In the original validation study, these classes were ordered by severity of kidney function loss as follows: focal, crescentic, mixed, and sclerotic. Subsequent validation studies disagreed on outcomes in the crescentic and mixed classes. This study, driven by the original investigators, provides several analyses in order to determine the current position of the histopathologic classification of ANCA-associated GN. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: A validation study was performed with newly collected data from 145 patients from ten centers worldwide, including an analysis of interobserver agreement on the histopathologic evaluation of the kidney biopsies. This study also included a meta-analysis on previous validation studies and a validation of the recently proposed ANCA kidney risk score. RESULTS: The validation study showed that kidney failure at 10-year follow-up was significantly different between the histopathologic classes (P<0.001). Kidney failure at 10-year follow-up was 14% in the crescentic class versus 20% in the mixed class (P=0.98). In the meta-analysis, no significant difference in kidney failure was also observed when crescentic class was compared with mixed class (relative risk, 1.15; 95% confidence interval, 0.94 to 1.41). When we applied the ANCA kidney risk score to our cohort, kidney survival at 3 years was 100%, 96%, and 77% in the low-, medium-, and high-risk groups, respectively (P<0.001). These survival percentages are higher compared with the percentages in the original study. CONCLUSIONS: The crescentic and mixed classes seem to have a similar prognosis, also after adjusting for differences in patient populations, treatment, and interobserver agreement. However, at this stage, we are not inclined to merge the crescentic and mixed classes because the reported confidence intervals do not exclude important differences in prognosis and because an important histopathologic distinction would be lost.

Renal relapse in antineutrophil cytoplasmic autoantibody-associated vasculitis: unpredictable, but predictive of renal outcome.

Objectives: To determine predictors of renal relapse and end-stage renal failure (ESRF) in patients with ANCA-associated vasculitis. Methods: Data from four European Vasculitis Society randomized controlled trials, conducted roughly simultaneously between 15 March 1995 and 30 September 2002, was pooled to determine predictors of long-term renal outcome. The respective trial inclusion criteria covered the entire spectrum of disease severity. Baseline predictors of time to first renal relapse and time to ESRF were assessed by competing events analysis and Cox proportional hazards regression. The effect of renal relapse on time to ESRF was assessed by adding renal relapses to the competing events analysis as a time-varying covariate. Results: The number of patients participating was 535; mean serum creatinine (±s.d.) at entry was 341 ± 321 µmol/l and 19.7% developed ESRF. One or more renal relapse(s) was experienced by 101 patients. Multivariable regression analysis demonstrated that, in addition to impaired baseline renal function, developing ⩾1 renal relapse was an independent risk factor for ESRF (subhazard ratio 9; 95% CI 4, 19; P < 0.001). No predictive factors for renal relapse were found. Conclusion: In addition to baseline renal function, the occurrence of renal relapses is an important determinant of ESRF in patients with ANCA-associated vasculitis. We did not find any clinical predictors for renal relapse itself, including disease activity elsewhere. In light of the silent nature of renal relapse in ANCA-associated vasculitis, we stress the need for long-term vigilant monitoring for early signs of renal relapse and propose performing 3-monthly urinalysis. This will enable timely treatment and help further improve renal outcome.

Investigations in systemic vasculitis - The role of renal pathology.

ANCA-associated vasculitis (AAV) describes a group of small-vessel vasculitides with frequent renal involvement. The first description of these conditions can be traced back to the 19th-century paper on necrotizing vasculitis by Kussmaul and Maier. Since then, our understanding of the pathogenesis has improved and the histopathological lesions have been described in detail. Characteristic histologic lesions in ANCA-associated glomerulonephritis (AAGN) are fibrinoid necrosis and crescents, often accompanied by tubulointerstitial inflammation. The discovery of ANCAs has not rendered renal biopsies obsolete in the diagnostic process. Currently, renal biopsies remain the gold standard for the diagnosis of AAV in conjunction with ANCA serology. In addition to diagnosis, renal biopsies are useful for patient prognosis. The evaluation of renal histological samples from patients with new-onset AAV who participated in clinical trials led to the proposal of the histopathological classification for AAGN. The prognostic value of this classification continues to be validated and an update is expected soon.

Anti-plasminogen antibodies in ANCA-associated vasculitis: An optimized anti-plasminogen assay.

Anti-plasminogen antibodies (α-PLG) were previously detected in a subpopulation of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) patients, showing a relation to renal lesions and outcome. Several studies showed different proportions of α-PLG positive AAV patients, possibly due to differences in the assays used. We here present a new, optimized α-PLG Enzyme-Linked Immuno Sorbent Assay (ELISA) and validate the presence of α-PLG in AAV. Different ELISA set-ups were tested regarding plasminogen (PLG) antigen, concentrations, coating buffers, blocking agents, and environmental conditions. Purified lysine-PLG (lys-PLG) showed better differentiation between positive samples and negative samples than glutamic acid-PLG (glu-PLG). Therefore, lys-PLG was used as coating antigen. With the optimized α-PLG ELISA we found α-PLG in 14.3% of the myeloperoxidase (MPO)-ANCA patients, whereas all our proteinase-3 (PR3)-ANCA patients tested in our new assay were negative. Concluding, in this study we have combined important technical findings and methods from previous studies to optimize the α-PLG assay, which can be used for future research purposes and will aid in uniform reporting of α-PLG status of patients.

Peripheral Neuropathy, Episodic Rhabdomyolysis, and Hypoparathyroidism in a Patient with Mitochondrial Trifunctional Protein Deficiency.

A combination of unexplained peripheral neuropathy, hypoparathyroidism, and the inability to cope with metabolic stress could point to a rare inborn error of metabolism, such as mitochondrial trifunctional protein (MTP) deficiency.Here, we describe a 20-year-old woman who was known since childhood with axonal motor sensory polyneuropathy of unknown origin. She presented with progressive dyspnoea, and increased muscle weakness, preceded by 6 days of fever, vomiting, and diarrhoea. Laboratory testing showed rhabdomyolysis, and hypocalcaemia with low parathyroid levels. The patient was intubated because of respiratory insufficiency and a viral and bacterial pneumonia was diagnosed. She was discharged after 16 days of admission. Metabolic screening, performed at the time of rhabdomyolysis, showed increased concentrations of long-chain 3-hydroxyacyl carnitine species, together with elevated urinary excretion of 3-hydroxy dicarboxylic acids. Decreased activity of long-chain 3-hydroxyacyl-CoA dehydrogenase and long-chain 3-ketoacyl-CoA thiolase in peripheral lymphocytes and fibroblasts confirmed a MTP deficiency. Sequence analysis of the HADHB gene showed two heterozygous variants: c.209+1G>C (splicing defect) and c.980T>C (p.Leu327Leu). When the acylcarnitine profile was repeated after the episode of rhabdomyolysis had resolved it showed no abnormalities.Our case illustrates a cluster of peripheral neuropathy, episodic rhabdomyolysis, and hypoparathyroidism in a patient with MTP deficiency caused by mutations in the HADHB gene. It stresses the importance of performing metabolic screening when patients are most symptomatic, as normal results can be found at times when no metabolic stress is present. Screening is relatively easy and timely diagnosis has important implications for treatment.

ANCA-Associated Glomerulonephritis: Risk Factors for Renal Relapse.

Relapse in ANCA-associated vasculitis (AAV) has been studied previously, but there are few studies on renal relapse in particular. Identifying patients at high risk of renal relapse may aid in optimizing clinical management. We investigated which clinical and histological parameters are risk factors for renal relapse in ANCA-associated glomerulonephritis (AAGN). Patients (n = 174) were newly diagnosed and had mild-moderate or severe renal involvement. Data were derived from two trials of the European Vasculitis Society: MEPEX and CYCAZAREM. The Cox regression model was used to identify parameters increasing the instantaneous risk (= rate) of renal relapse (useful for instant clinical decisions). For identifying predictors of renal relapse during follow-up, we used Fine & Gray's regression model. Competing events were end-stage renal failure and death. The cumulative incidence of renal relapse at 5 years was 9.5% (95% CI: 4.8-14.3%). In the Cox model, sclerotic class AAGN increased the instantaneous risk of renal relapse. In Fine & Gray's model, the absence of interstitial infiltrates at diagnosis was predictive for renal relapse. In this study we used two different models to identify possible relationships between clinical and histopathological parameters at time of diagnosis of AAV with the risk of experiencing renal relapse. Sclerotic class AAGN increased the instantaneous risk of renal relapse. This association is most likely due to the high proportion of sclerosed glomeruli reducing the compensatory capacity. The absence of interstitial infiltrates increased the risk of renal relapse which is a warning sign that patients with a relatively benign onset of disease may also be prone to renal relapse. Renal relapses occurring in patients with sclerotic class AAGN and renal relapses occurring in patients without interstitial infiltrates were mutually exclusive, which may indicate that they are essentially different.

The Dutch Transplantation in Vasculitis (DUTRAVAS) Study: Outcome of Renal Transplantation in Antineutrophil Cytoplasmic Antibody-associated Glomerulonephritis.

BACKGROUND: Data on the outcome of renal transplantation in antineutrophil cytoplasmic antibody-associated glomerulonephritis (AAGN) patients are still limited. In particular, how disease recurrence in the renal allograft defines graft outcome is largely unknown. Therefore, we conducted a multicenter observational clinical and histopathological study to establish recurrence rate of AAGN in the allograft and the impact of recurrence on allograft survival. METHODS: Using the nationwide Dutch Pathology Registry (PALGA), we retrospectively collected clinical and histopathological data of consecutive AAGN patients who had developed end-stage renal failure and received a kidney allograft in 1 of 6 Dutch university hospitals between 1984 and 2011. Transplant biopsies were scored using the Banff '09 classification. Renal disease recurrence was scored using the histopathological classification of AAGN. RESULTS: The posttransplantation recurrence rate of AAGN was 2.8% per patient year, accumulating to recurrence in a total of 11 of 110 AAGN patients within the first 5 years after transplantation. Four of these 11 patients lost their graft, with 1-year and 5-year graft survival rates of 94.5% and 82.8%, respectively. By multivariate analysis, AAGN recurrence was independently associated with subsequent graft loss. CONCLUSIONS: In this study in 110 Dutch patients, the recurrence rate of AAGN within 5 years after kidney transplantation appeared slightly higher than in previous reports. Moreover, recurrence of AAGN contributed independently to kidney allograft loss, emphasizing the importance of clinical vigilance, because early treatment might be critical to rescuing the allograft.

Incidence of Malignancies in Patients With Antineutrophil Cytoplasmic Antibody-Associated Vasculitis Diagnosed Between 1991 and 2013.

OBJECTIVE: To investigate the incidence of malignancies during longitudinal followup of patients with antineutrophil cytoplasmic antibody-associated vasculitis (AAV), and to examine the effect of immunosuppressive therapy on malignancy risk in these patients. METHODS: The study population consisted of patients with histopathologically confirmed AAV, diagnosed between 1991 and 2013 at a large university hospital. The mean duration of followup was 10 years. Malignancy incidence was assessed using the Dutch National Pathology Database. Incidence rates from the Netherlands Cancer Registry were used to compare malignancy incidence in the AAV cohort to that in the general Dutch population. RESULTS: Thirty-six of 138 patients with AAV developed a total of 85 malignancies during a mean followup of 9.7 years. The sex-, age-, and calendar year-adjusted malignancy risk was 2.21-fold higher (95% confidence interval [95% CI] 1.64-2.92) than that in the general population. Non-melanoma skin cancers occurred most frequently (standardized incidence ratio 4.23 [95% CI 2.76-6.19]). The incidence rates of other malignancies were not significantly increased. Malignancy risk was associated with the duration of cyclophosphamide (CYC) therapy and, interestingly, was not increased in patients who had received CYC for <1 year. CONCLUSION: Patients with AAV have a higher risk of malignancy than the general population, but this risk is accounted for solely by non-melanoma skin cancers. Over the years, the risk of other malignancies-specifically bladder and hematologic malignancies-has decreased in patients with AAV. This finding reflects ongoing efforts to reduce CYC exposure by developing new treatment regimens.

Renal function and ear, nose, throat involvement in anti-neutrophil cytoplasmic antibody-associated vasculitis: prospective data from the European Vasculitis Society clinical trials.

OBJECTIVE: We investigated whether ENT involvement is associated with renal biopsy findings and renal function in patients with ANCA-associated vasculitis (AAV). METHODS: Newly diagnosed AAV patients derived from three international, multicentre trials were included. To investigate an association between ENT involvement and estimated glomerular filtration rate (eGFR) at diagnosis and 5-year follow-up, we performed multivariable regression analyses including clinical and histopathological parameters. To investigate whether our findings are specific to ENT involvement, we performed comparable analyses between eGFR and other early disease manifestations (arthralgia/arthritis, cutaneous and lung involvement). RESULTS: One hundred and eighty-five of the 414 patients had ENT involvement. The mean presenting eGFR of patients with and without ENT involvement was 39.16 and 23.88 ml/min/1.73 m(2), respectively (P < 0.001). Mean eGFR increased by 6.76 ml/min/1.73 m(2) with each added ENT symptom (P = 0.007). Patients with ENT involvement had less interstitial fibrosis and tubular atrophy and a prognostically more favourable histopathological class on renal biopsy examination. Multivariable regression analyses correcting for clinical and histopathological parameters showed that ENT involvement is associated with both baseline and 5-year follow-up eGFR. There were no associations between baseline and 5-year follow-up eGFR and arthralgia/arthritis, cutaneous or lung involvement, suggesting that our findings are specific to ENT involvement. CONCLUSION: The presence of ENT involvement in AAV patients is associated with prognostically favourable renal biopsy findings and better renal function. These results indicate that there may be different phenotypes of AAV defined by ENT involvement.

Repeat protocol renal biopsy in ANCA-associated renal vasculitis.

BACKGROUND: Histopathological lesions in renal biopsy (RB) at presentation of ANCA-associated vasculitis (AAV) have been described in depth but repeat protocolized renal biopsies are seldomly performed in AAV. In this study, we present a group of AAV patients with repeat protocolized biopsies, and we evaluate their clinical significance. METHODS: A total of 17 consecutive patients diagnosed between 1991 and 1995 with AAV and renal involvement confirmed by biopsy at presentation in a single center underwent a protocol planned rebiopsy in remission after a median of 13 months (range 11-28) from diagnosis. Biopsies were assessed by two independent pathologists, blinded to patient data. Clinical data were collected retrospectively. RESULTS: Patients were followed-up for a median of 189 months from diagnosis. Renal relapse was observed in eight patients (47.1%), seven patients died, three patients reached end-stage renal failure. There was a significant decrease in the percentage of acute lesions (cellular crescents, fibrinoid necrosis, P < 0.001) and a significant increase in chronic lesions (glomerulosclerosis, interstitial fibrosis, P ≤ 0.01) in the repeat RB compared with the first RB. This resulted in a class change over the biopsies within most patients. The percentage of normal glomeruli in the first biopsy positively correlated with estimated GFR at the end of follow-up (rs = 0.509, P = 0.05). CONCLUSIONS: This is the first study on protocolized repeat biopsies in AAV, giving insight into disease activity under immunosuppressive treatment. Apparently, many AAV patients have grumbling disease with ongoing activity, eventually leading to an increased amount of chronic lesions.

Tubular lesions predict renal outcome in antineutrophil cytoplasmic antibody-associated glomerulonephritis after rituximab therapy.

Histopathological features in renal biopsies of patients with antineutrophil cytoplasmic antibody-associated vasculitis have predictive value for renal outcome in patients who receive standard treatment with cyclophosphamide and corticosteroids; however, whether the same holds true for rituximab-treated patients is unknown. We describe associations between renal histopathology and outcomes among patients treated with a rituximab-based regimen in the Randomized Trial of Rituximab versus Cyclophosphamide in ANCA-Associated Vasculitis trial. Two pathologists, blinded to clinical data, reviewed biopsies from 30 patients according to a standardized protocol that included assessment of T cell, B cell, and plasma cell infiltration, as well as scoring for tubulitis, interstitial inflammation, and glomerulitis. We did not observe associations between immunohistology scores and age, sex, estimated GFR at entry, or requirement for dialysis. However, tubulointerstitial inflammation was more severe among patients who had a positive test for the myeloperoxidase antineutrophil cytoplasmic antibody. In a multiple linear regression model, both CD3(+) T cell tubulitis and tubular atrophy independently associated with estimated GFR at 12 months. Tubular atrophy remained an independent predictor at 24 months (P<0.01). These results suggest that in addition to anti-B cell therapy, therapy directed at T cells may improve renal outcomes in antineutrophil cytoplasmic antibody-associated vasculitis.

Anti-plasminogen antibodies compromise fibrinolysis and associate with renal histology in ANCA-associated vasculitis.

Antibodies recognizing plasminogen, a key component of the fibrinolytic system, associate with venous thrombotic events in PR3-ANCA vasculitis. Here, we investigated the prevalence and function of anti-plasminogen antibodies in independent UK and Dutch cohorts of patients with ANCA-associated vasculitis (AAV). We screened Ig isolated from patients (AAV-IgG) and healthy controls by ELISA. Eighteen of 74 (24%) UK and 10/38 (26%) Dutch patients with AAV had anti-plasminogen antibodies compared with 0/50 and 1/61 (2%) of controls. We detected anti-plasminogen antibodies in both PR3-ANCA- and MPO-ANCA-positive patients. In addition, we identified anti-tissue plasminogen activator (tPA) antibodies in 13/74 (18%) patients, and these antibodies were more common among patients with anti-plasminogen antibodies (P = 0.011). Eighteen of 74 AAV-IgG (but no control IgG) retarded fibrinolysis in vitro, and this associated with anti-plasminogen and/or anti-tPA antibody positivity. Only 4/18 AAV-IgG retarded fibrinolysis without harboring these antibodies; dual-positive samples retarded fibrinolysis to the greatest extent. Patients with anti-plasminogen antibodies had significantly higher percentages of glomeruli with fibrinoid necrosis (P < 0.05) and cellular crescents (P < 0.001) and had more severely reduced renal function than patients without these antibodies. In conclusion, anti-plasminogen and anti-tPA antibodies occur in AAV and associate with functional inhibition of fibrinolysis in vitro. Seropositivity for anti-plasminogen antibodies correlates with hallmark renal histologic lesions and reduced renal function. Conceivably, therapies that enhance fibrinolysis might benefit a subset of AAV patients.

Histopathologic classification of ANCA-associated glomerulonephritis.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is the most common cause of rapidly progressive glomerulonephritis worldwide, and the renal biopsy is the gold standard for establishing the diagnosis. Although the prognostic value of the renal biopsy in ANCA-associated glomerulonephritis is widely recognized, there is no consensus regarding its pathologic classification. We present here such a pathologic classification developed by an international working group of renal pathologists. Our classification proposes four general categories of lesions: Focal, crescentic, mixed, and sclerotic. To determine whether these lesions have predictive value for renal outcome, we performed a validation study on 100 biopsies from patients with clinically and histologically confirmed ANCA-associated glomerulonephritis. Two independent pathologists, blinded to patient data, scored all biopsies according to a standardized protocol. Results show that the proposed classification system is of prognostic value for 1- and 5-year renal outcomes. We believe this pathologic classification will aid in the prognostication of patients at the time of diagnosis and facilitate uniform reporting between centers. This classification at some point might also provide means to guide therapy.