Waning humoral immunity of SARS-CoV-2 vaccination in a rheumatoid arthritis cohort and the benefits of a vaccine booster dose.

OBJECTIVES: We aimed to assess SARS-CoV-2 spike-specific antibody kinetics postvaccination and the benefit of a mRNA vaccine booster dose in rheumatoid arthritis (RA) patients treated with immunosuppressive drugs. METHODS: Consecutive RA patients on immunosuppressive therapies, with no known history of SARS-CoV-2 infection or high-risk contact, vaccinated with 2 doses SARS-CoV-2 mRNA, BNT162b2 or mRNA-1273, or viral vectored ChAdOx1 nCoV-19 vaccine were recruited during their routine rheumatology consultation. Anti-SARS-CoV-2 IgG spike-specific antibodies were quantified at 1, 3 and 6 months respectively following the second vaccine dose. The incidence of SARS-CoV-2 infection post-vaccination during this 6-month longitudinal study was also assessed. RESULTS: Of the 104 RA patients included, 79 patients completed the 6-month trial follow-up. A significant decrease in anti-SARS-CoV-2 spike-specific IgG titres was observed between 1-month and 3-month postvaccination (p<0.01). Among the 46 patients (46/79) receiving a booster dose, all developed detectable anti-SARS-CoV-2 spike-specific IgG antibodies at the 6-month follow-up with significantly higher titres compared to 1-month (p<0.001) and 3-month (p<0.0001) post-vaccination. Conversely, the antibody titres among the 33 patients (33/79) not receiving a booster dose decreased significantly at the 6-month follow-up compared to 1-month (p<0.0001) and 3-month (p<0.01) post-vaccination. The incidence of COVID-19 disease postvaccination was 8.9% without severe forms. CONCLUSIONS: To our knowledge, this is the first study to report on anti-SARS-CoV-2 spike-specific antibody kinetics postvaccination and the effect of a booster dose in a cohort of RA patients. The latter is essential given the waning humoral immunity observed in vaccinated RA patients and the increased incidence of COVID-19 diseases postvaccination in this 6-month longitudinal study.

Neuromyelitis Optica: Pathogenesis Overlap with Other Autoimmune Diseases.

PURPOSE OF REVIEW: Neuromyelitis optica (NMO) is an auto-immune disease essentially depicted by optic neuritis and transverse myelitis. Per se, NMO was initially believed to be a sub-type of multiple sclerosis with typical demyelinating cerebral lesions and optic nerve inflammation. More recently, corroborating lignes of evidence have strengthened the concept of the spectrum of diseases associated with NMO and more specifically with the role of anti-aquaporin-4 antibodies in the pathogenesis of disease. RECENT FINDINGS: In this article, we review the recent pathogenic findings in NMO and more interestingly the newly discovered role of anti-aquaporin-4 antibodies as key players in triggering cerebral lesions. The concept of spectrum of diseases associated with NMO is also discussed. These recent findings have paved in the further understanding of the pathogenesis underlying NMO and new treatments are currently being developed targeting anti-aquaporin-4 antibodies.

Involvement of Epithelial-Mesenchymal Transition (EMT) in Autoimmune Diseases.

Epithelial-mesenchymal transition (EMT) is a complex reversible biological process characterized by the loss of epithelial features and the acquisition of mesenchymal features. EMT was initially described in developmental processes and was further associated with pathological conditions including metastatic cascade arising in neoplastic progression and organ fibrosis. Fibrosis is delineated by an excessive number of myofibroblasts, resulting in exuberant production of extracellular matrix (ECM) proteins, thereby compromising organ function and ultimately leading to its failure. It is now well acknowledged that a significant number of myofibroblasts result from the conversion of epithelial cells via EMT. Over the past two decades, evidence has accrued linking fibrosis to many chronic autoimmune and inflammatory diseases, including systemic sclerosis (SSc), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjögren's syndrome (SS), and inflammatory bowel diseases (IBD). In addition, chronic inflammatory states observed in most autoimmune and inflammatory diseases can act as a potent trigger of EMT, leading to the development of a pathological fibrotic state. In the present review, we aim to describe the current state of knowledge regarding the contribution of EMT to the pathophysiological processes of various rheumatic conditions.

Soluble ST2 is increased in systemic lupus erythematous and is a potential marker of lupus nephritis.

OBJECTIVES: To investigate the role of the interleukin IL-33/ST2 axis in systemic lupus erythematosus (SLE). METHODS: Serum concentrations of IL-33 and sST2 were measured by sandwich ELISA in SLE patients (n=111) compared to sex- and age-matched healthy controls (n=36). The serum concentrations of IL-33 and sST2 were correlated with various clinical and biological parameters. The expressions of IL-33 and ST2L were investigated in kidney sections by immunohistochemistry in lupus nephritis patients (n=23) and controls (n=10). RESULTS: Serum levels of IL-33 were significantly higher in SLE patients (11.64±3.141 pg/mL) than in controls (1.043±0.8526 pg/mL) (p<0.0001). Similarly, the serum concentrations of sST2 were significantly higher in SLE patients (34.013±2.043 pg/mL) than in controls (25.278±2.258 pg/mL) (p=0.046). sST2, but not IL-33, correlated significantly with disease activity index (SLEDAI). In addition, serum levels of sST2 were significantly higher in patients with lupus nephritis (45.438±5.661 pg/mL) that in SLE patients without renal involvement (30.691±1.941 pg/mL) (p=0.016). The immunoreactivity of IL-33 in renal biopsies of patients with lupus nephritis was not increased compared to controls, while the glomerular expression of ST2L was significantly higher in nephritis patients compared to controls. CONCLUSIONS: Although IL-33 and sST2 levels are both increased in SLE, sST2 represents a surrogate marker of disease activity and complications of nephritis.

Assessment of sarcopenia in patients with fibromyalgia.

Fibromyalgia is a chronic disorder characterized by persistent widespread musculoskeletal pain. Patients with fibromyalgia have reduced physical activity and increased sedentary rate. The age-associated reduction of skeletal muscle mass and function is called sarcopenia. The European Working Group on Sarcopenia in Older People developed a practical clinical definition and consensus diagnostic criteria for sarcopenia. Loss of muscle function is common in fibromyalgia and in the elderly. The goal of this study is to determine whether the reduction of muscle function in fibromyalgia is related to sarcopenia according to the European Working Group on Sarcopenia in Older People criteria. Forty-five patients with fibromyalgia and thirty-nine healthy control female subjects were included. All the participants were assessed by Fibromyalgia Impact Questionnaire and SARC-F questionnaire. Muscle mass was evaluated by bioimpedance analysis, muscle strength by handgrip strength test and physical performance with the Short Physical Performance Battery. Fibromyalgia Impact Questionnaire and SARC-F scores were statistically significantly higher in the fibromyalgia group than in the control group, showing severe disease and a higher risk of sarcopenia in the fibromyalgia group (p < 0.001). Muscle strength and physical performance were statistically significantly lower in the group with fibromyalgia than in the control group (p < 0.001). There was no statistical difference between fibromyalgia and control groups regarding skeletal muscle mass (p = 0.263). Our study demonstrated a significant reduction in muscle function in fibromyalgia patients without any loss of muscle mass. Loss of muscle function without decrease in muscle mass is called dynapenia.

A Training Tool to support the management and diagnosis of Sjögren's syndrome.

OBJECTIVES: The objective of this work is to present a Training Tool designed to support healthcare professionals involved in the diagnosis and management of Sjögren's syndrome. METHODS: The Training Tool aims to fulfil the gap of targeted education by providing a structured protocol of training including state of the art guidelines and practices. For the development of the Training Tool, latest relevant technologies have been used to assure efficiency and usability. Core functionalities include training by a series of multimedia courses, testing during the learning process, and profiling for monitoring the progress. An iterative requirement analysis process was established involving a large number of clinical experts, with the objective to identify user's training needs. RESULTS: Comprehensive usability evaluation was performed by applying, an Unmoderated Remote Usability Test resulting to 97.2% Success Rate; and the well-established System Usability Scale, reaching a score of 90.4 which classifies the Training Tool as "A" graded-excellent. CONCLUSIONS: The Training Tool offers open-online training of healthcare professionals involved in the diagnosis and management of Sjögren's syndrome, using a well-designed training protocol in highly usable manner. To our knowledge, this is the first such tool for Sjögren's syndrome.

Phagocyte-specific S100A8/A9 is upregulated in primary Sjögren's syndrome and triggers the secretion of pro-inflammatory cytokines in vitro.

OBJECTIVES: To determine the role of S100A8/A9 in the pathogenesis of primary Sjögren's syndrome (pSS). METHODS: The serum levels of S100A8/A9 were determined in pSS patients and healthy controls by ELISA. The expression of S100A8/A9 in salivary glands was assessed by immunohistochemistry. The phenotype of S100A8+ and S100A9+ cells was identified using double immunofluorescence. The effects of S100A8/A9 on cytokine production by peripheral blood mononuclear cells (PBMCs) from pSS patients were determined in vitro by flow cytometry. The effects of pro-inflammatory cytokines on S100A8/A9 secretion were additionally investigated in vitro by ELISA in PBMCs from pSS patients and control subjects. RESULTS: Serum levels of S100A8/A9 were significantly increased in pSS patients compared to healthy controls. The tissular expression of S100A8 and S100A9, identified in professional phagocytes (neutrophils, monocytes and plasmacytoid dendritic cells), was increased in the salivary glands of pSS patients and correlated with focus score. In vitro, recombinant S100A8/A9 increased the production of IL-1ß, IL-6, TNF-α, IFN-γ, IL-10, IL-17A and IL-22 by PBMCs. The S100A8/A9-induced increase in TNF-α production in pSS patients was significant relative to controls. Furthermore, IL-1ß, TNF-α, IL-6, and IL-17A stimulated release of S100A8/A9 from PBMCs in pSS patients. CONCLUSIONS: S100A8/A9 is increased in pSS patients contributing to the in vitro increased production of pro-inflammatory cytokines. As such, S100A8/A9 in concert with other cytokines might contribute to the pathogenesis of pSS.

Adenosine triphosphate prevents serum deprivation-induced apoptosis in human mesenchymal stem cells via activation of the MAPK signaling pathways.

Human mesenchymal stem cells (hMSC) are multipotent cells derived from various sources including adipose and placental tissues as well as bone marrow. Owing to their regenerative and immunomodulatory properties, their use as a potential therapeutic tool is being extensively tested. However, one of the major hurdles in using cell-based therapy is the use of fetal bovine serum that can trigger immune responses, viral and prion diseases. The development of a culture medium devoid of serum while preserving cell viability is therefore a major challenge. In this study, we demonstrated that adenosine triphosphate (ATP) restrained serum deprivation-induced cell death in hMSC by preventing caspases 3/7 activation and modulating ERK1/2 and p38 MAPK signaling pathways. We also showed that serum deprivation conditions triggered dephosphorylation of the proapoptotic protein Bad leading to cell death. Adjunction of ATP restored the phosphorylation state of Bad. Furthermore, ATP significantly modulated the expression of proapoptopic and antiapoptotic genes, in favor of an antiapoptotic profile expression. Finally, we established that hMSC released a high amount of ATP in the extracellular medium when cultured in a serum-free medium. Collectively, our results demonstrate that ATP favors hMSC viability in serum deprivation conditions. Moreover, they shed light on the cardinal role of the MAPK pathways, ERK1/2 and p38 MAPK, in promoting hMSC survival.

Potential involvement of the IL-33-ST2 axis in the pathogenesis of primary Sjogren's syndrome.

OBJECTIVES: To investigate the role of the interleukin (IL)-33-ST2 axis in the pathophysiology of primary Sjögren's syndrome (pSS). METHODS: Serum levels of IL-33 and sST2 were determined by ELISA. The expression of IL-33 and ST2 was investigated in salivary glands (SG) by immunohistochemistry. PBMC were isolated and stimulated with IL-33, IL-12 and IL-23 and the cytokine profile response was examined by flow cytometry. Intracellular cytokine detection of IFNγ and IL-17 was performed by flow cytometry. RESULTS: Serum IL-33 and sST2 levels were increased in pSS patients compared with controls and patients with systemic lupus erythematosus. Expression of IL-33 was upregulated in SG with Chisholm scores of 2 and 3 of pSS patients but comparable with controls for SG with Chisholm score of 4. ST2 expression in SG was downregulated in pSS patients. IL-33 at different concentrations did not increase the secretion of pro-inflammatory cytokines but acted synergistically with IL-12 and IL-23 to promote IFNγ production. NK and NKT cells were identified as main producers of IFNγ in vitro and were found in SG of pSS patients. CONCLUSIONS: IL-33 is released in pSS, and acts with IL-12 and IL-23 to favour the secretion of IFNγ by NK and NKT cells.

Clinical Profile of Patients with Primary Sjögren's Syndrome with Non-Identified Antinuclear Autoantibodies.

Objectives-The aim of the present study was to characterize the clinical phenotype of patients with primary Sjögren's syndrome (pSS) with non-identified antinuclear antibodies (ANA) in comparison with that of patients with pSS with negative ANA, positive typical ANA (anti-Ro/SSA and/or La/SSB) and positive atypical ANA. Methods-We conducted an observational, retrospective monocentric study at the Erasme University Hospital (Brussels, Belgium). Two hundred and thirty-three patients fulfilling the 2002 American-European Consensus Group criteria for pSS were included in this study. The patients were subdivided according to their ANA profile and demographics. The clinical and biological data of each subgroup were compared. Moreover, the relationships between these data and the ANA profiles were determined by multiple correspondence analysis. Results-In our cohort, 42 patients (18%) presented a non-identified ANA-positive profile. No statistically significant difference could be observed between non-identified ANA patients and ANA-negative patients in terms of age and/or ESSDAI score at diagnosis. There were significantly more frequent articular manifestations, positive rheumatoid factor (RF), and the use of corticosteroids in anti-Ro/SSA-positive patients compared to ANA-negative (p ≤ 0.0001) and non-identified ANA-positive patients (p ≤ 0.01). However, a significantly higher proportion of RF positivity and corticosteroid treatment was observed in non-identified ANA-positive patients compared to ANA-negative patients (p < 0.05). Conclusions-For the first time to our knowledge, our study has characterized the clinical phenotype of patients with pSS with non-identified ANA at diagnosis. The non-identified ANA-positive patients featured mostly a clinical phenotype similar to that of the ANA-negative patients. On the other hand, the non-identified ANA-positive patients were mainly distinguished from the ANA-negative patients by a greater proportion of RF positivity and the need for corticosteroid use due to articular involvement.

Cryofibrinogen levels are increased in non-traumatic osteonecrosis: a new pathogenic clue to osteonecrosis?

OBJECTIVE: To determine whether levels of cryofibrinogen are increased in non-traumatic osteonecrosis (ON) and could correlate with disease staging. METHODS: We prospectively analysed cryofibrinogen levels by immunofixation electrophoresis in 50 patients with non-traumatic ON, 50 healthy volunteers and 8 patients with traumatic ON. Staging of disease involving the femoral heads and the size of necrotic lesions were assessed by the Association Research Circulation Osseous (ARCO) classification system. RESULTS: Mean cryofibrinogen levels in patients with non-traumatic ON were significantly increased relative to healthy controls and to patients with traumatic ON (222.1 ± 20.6, 59.9 ± 5.6 and 52.3 ± 14.9 mg/dl, respectively, P < 0.001). In the non-traumatic ON group, mean cryofibrinogen levels were significantly increased in patients with multifocal ON compared with patients with mono/bifocal ON (276.5 ± 56.5 and 149.3 ± 15.4 mg/dl, respectively, P = 0.03). There were no significant differences in cryofibrinogen levels observed with respect to the size of the necrotic lesions involving the femoral heads. Moreover, cryofibrinogen levels in patients with ON of the femoral heads classified according to the stage of disease were not significantly different between patients with stage 1/2 and patients with stage 3 ON (179.2 ± 31.3 vs 204.1 ± 29.0 mg/dl, respectively; P = 0.813). CONCLUSION: Cryofibrinogen levels are increased in non-traumatic ON and, more importantly, in multifocal ON. The fact that cryofibrinogen levels are not correlated with the size of lesions and the stage of disease could imply systemic rather than local involvement characterizing the pathogenesis of ON.

Involvement of aquaporin 5 in Sjögren's syndrome.

Sjögren's syndrome (SS) is a chronic autoimmune disease with the pathological hallmark of lymphoplasmacytic infiltration of exocrine glands - more specifically salivary and lacrimal glands - resulting in a diminished production of tears and saliva (sicca syndrome). The pathophysiology underscoring the mechanisms of the sicca symptoms in SS has still yet to be unraveled but recent advances have identified a cardinal role of aquaporin-5 (AQP5) as a key player in saliva secretion as well as salivary gland epithelial cell dysregulation. AQP5 expression and localization are significantly altered in salivary glands from patients and mice models of the disease, shedding light on a putative mechanism accounting for diminished salivary flow. Furthermore, aberrant expression and localization of AQP5 protein partners, such as prolactin-inducible protein and ezrin, may account for altered AQP5 localization in salivary glands from patients suffering from SS and are considered as new players in SS development. This review provides an overview of the role of AQP5 in SS salivary gland epithelial cell dysregulation, focusing on its trafficking and protein-protein interactions.

Pathophysiologic role of Interleukin-33/ST2 in Sjögren's syndrome.

Interleukin-33 (IL-33) is a member of the IL-1 family and has dual functions as a nuclear factor as well as a cytokine. The pivotal role of IL-33 as an active player contributing to aberrant local and systemic damage has been highlighted in several inflammatory and autoimmune diseases. Primary Sjögren's syndrome (pSS) is an autoimmune disease characterized by dry eyes and mouth syndrome due to local dysfunctions of exocrine glands, but also accompanied with systemic manifestations. The pathophysiology of pSS has been advocated as a conjecture of activated B and T cells as well as the production of inflammatory cytokines and autoantibodies, driving epithelial tissue damage and disease progression. In pSS, IL-33 is released in the extracellular space from damaged salivary cells upon pro-inflammatory stimuli and/or dysfunction of epithelial barrier. Counter-regulatory mechanisms are initiated to limit the pro-inflammatory actions of IL-33 as portrayed by an increase in the decoy receptor for IL-33, the soluble form of ST2 (sST2). In pSS and associated diseases, the levels of IL-33 are significantly elevated in the serum or tears of patients. Mechanistically, IL-33 acts in synergy with IL-12 and IL-23 on NK and NKT cells to boost the production of IFN-γ contributing to inflammation. TNF-α, IL-1ß and IFN-γ in turn further increase the activation of IL-33/ST2 pathway, thereby constituting a vicious inflammatory loop leading to disease exacerbation. IL-33/ST2 axis is involved in Sjögren's syndrome and opens new perspectives as therapeutic target of one of the culprits in the inflammatory perpetuation.

Clinical course of COVID-19 infection in inflammatory rheumatological patients: a monocentric Belgian experience.

OBJECTIVE: Little is known about the incidence and consequences of coronavirus disease 2019 (COVID-19) infection in patients with rheumatic diseases. To improve our knowledge in this field, we collected data from patients with inflammatory rheumatic diseases who developed COVID-19 infection. METHODS: We performed a monocentric observational longitudinal study and collected data retrospectively from patients with inflammatory rheumatic diseases who developed a confirmed or suspected COVID-19 infection between 3 March and 10 June 2020. RESULTS: A total of 23 patients developed COVID-19 infection. Seven patients needed hospitalization [female 57%, mean age 59 +/- 9 years], and 16 patients were followed as outpatients [female 80%, mean age 50 +/- 14 years]. All hospitalized patients had more than one co-morbidity. At the time of infection, all patients were on immunosuppressive therapy consisting of either conventional synthetic DMARDs and/or biotherapy, with or without CSs. A minority received Corticoids (CSs) only. The most common symptoms of COVID-19-infected patients were fever, dyspnoea, cough and fatigue. PCR and chest CT were performed in all hospitalized patients to confirm the diagnosis (100% positive PCR, 71% positive CT). All outclinic patients were diagnosed clinically (confirmed by PCR in only one). The mean length of hospital stay was 21 +/- 19 days. Three patients developed an ARDS, including one who died. CONCLUSION: A limited number of patients with inflammatory rheumatic diseases suffered from COVID-19 infection. Two patients needed mechanical ventilation and survived, whereas one patient died. All patients with a severe form of infection had at least one co-morbidity.

Non traumatic osteonecrosis of the femoral head is associated with low bone mass.

OBJECTIVE: Osteoporosis (OP) and osteonecrosis of the femoral head (ONFH) share common clinical and pathophysiological features we sought to determine whether ONFH was associated with an increased prevalence of OP and whether the increased prevalence of OP was related to the stage of ONFH at diagnosis. METHODS: We included 243 patients with ONFH and 399 age and sex-matched healthy controls. Data was gathered including demography, risk factors, ARCO staging of ONFH and bone mineral density (BMD). RESULTS: Overall, BMD (defined by the T-score) was significantly lower in the ONFH group at both the femoral head (-0.96±1.11) and the lumbar spine (-1.22±1.47) compared to the control group (-0.55±0.97 and -0.73±1.31) (p<0.01). The ONFH group depicted a significantly higher proportion of osteopenia (50.39% vs 40.87%, p=0.027) and of OP (18.78% vs 7.33%, p<0.001) relative to the control group. Stage 1 and 2 ONFH patients (53.86%, p=0.0203; OR=1.54 (95% CI: [1.04; 2.29])) were at a higher risk of osteopenia than the control group (40.88%), but not stages 3 or 4 (48.47%, p=0.2569; OR=1.27 (95% CI: [0.78; 2.06]). Patients with stage 3 or 4 ONFH (25.31%, p<0.001; OR=3.93 (95% CI: [1.63; 10.96])) were at a higher risk of osteoporosis than patients in the stage 1 and 2 ONFH (7.24%), and compared to the control group (7.33%, adj. p-value<0.001; OR=4.89 (95% CI: [2.77; 8.76]). CONCLUSIONS: Non-traumatic osteonecrosis of the femoral heads is associated with low bone mineral density. This study showed that fractural stages ONFH were associated with a 5-fold risk of osteoporosis.

Efficacy of golimumab in Belgian patients with active rheumatoid arthritis despite treatment with non-biologic disease-modifying anti-rheumatic drugs: sub-analysis of the GO-MORE study.

OBJECTIVES: The GO-MORE trial (NCT00975130) was a phase 3 study in 40 countries evaluating the efficacy and safety of golimumab as add-on therapy in biologic-naïve adults with active rheumatoid arthritis despite stable treatment with disease-modifying anti-rheumatic drugs. To inform local practice in Belgium and examine the role of baseline disease activity in treatment response, we compared the efficacy of golimumab in the Belgian subpopulation and the rest of the world. METHODS: Baseline disease activity and six-month efficacy rates in the GO-MORE trial were compared for the Belgian subpopulation and the rest of the world by t-tests and chi-squared tests. RESULTS: Except for functional impairment, all measures of baseline disease activity were significantly lower (p < 0.0001) in the Belgian population (n = 123) than in the rest of the world (n = 3157). At month six, the rate of good/moderate EULAR response was similar in Belgium and the rest of the world (78.9% vs. 82.2%; p = 0.34), but remission rates were higher in Belgium according to the DAS28-ESR (43.1% vs. 23.2%; p < 0.0001) and Simplified Disease Activity Index (22.0% vs. 13.8%; p = 0.01). Rates of low DAS28-ESR disease activity were also higher in Belgium (54.5% vs. 36.8%; p < 0.0001). Within the Belgian subpopulation, efficacy measures were not significantly different between patients with moderate (n = 73) and high baseline activity (n = 49). Rates of functional impairment at month six did not differ between the two populations. CONCLUSION: In the Belgian population of the GO-MORE trial, baseline disease activity was lower and six-month remission rates were higher than in the rest of the world.

Value of non-identified ANCA (non-PR3, non-MPO) in the diagnosis of granulomatosis with polyangiitis (Wegener's granulomatosis).

OBJECTIVE: Determine the frequency of granulomatosis with polyangiitis (GPA) associated with non-identified ANCA (non-MPO, non-PR3 ANCA) and secondarily compare their clinic with GPA associated with MPO-positive or PR3-positive ANCA. METHODS: In a monocentric retrospective observational study, clinical data of 398 patients with non-identified ANCA (titer of ANCA at least 1/80 by immunofluorescence on ethanol fixed PMN) was gathered over a period of 6 years. GPA patients from this population were compared with GPA patients with identified ANCA on the basis of clinical, biological, immunological and histological features. RESULTS: The most common diseases associated with non-identified ANCA were inflammatory bowel diseases accounting for 17% of diseases. GPA accounted for only 1.8% of cases. There were no significant differences in terms of clinical and histological characteristics between GPA with non-identified ANCA and GPA with identified ANCA, but significantly higher CRP levels were observed in GPA patients with identified ANCA (p = 0.005). Localized disease (ear, nose and throat and/or lung involvement without any other systemic involvement) was more frequent in the group of GPA with nonidentified ANCA (p = 0.047) as compared to GPA with identified ANCA. This explains that the former group of patients was less frequently treated by cyclophosphamide than the latter (p = 0.016). CONCLUSION: GPA with non-MPO, non-PR3 ANCAs is relatively rare. Our study suggests that GPA with nonidentified ANCA differs from GPA with identified ANCA by the frequency of localized forms.