Serum-circulating His-tRNA synthetase inhibits organ-targeted immune responses.

His-tRNA synthetase (HARS) is targeted by autoantibodies in chronic and acute inflammatory anti-Jo-1-positive antisynthetase syndrome. The extensive activation and migration of immune cells into lung and muscle are associated with interstitial lung disease, myositis, and morbidity. It is unknown whether the sequestration of HARS is an epiphenomenon or plays a causal role in the disease. Here, we show that HARS circulates in healthy individuals, but it is largely undetectable in the serum of anti-Jo-1-positive antisynthetase syndrome patients. In cultured primary human skeletal muscle myoblasts (HSkMC), HARS is released in increasing amounts during their differentiation into myotubes. We further show that HARS regulates immune cell engagement and inhibits CD4+ and CD8+ T-cell activation. In mouse and rodent models of acute inflammatory diseases, HARS administration downregulates immune activation. In contrast, neutralization of extracellular HARS by high-titer antibody responses during tissue injury increases susceptibility to immune attack, similar to what is seen in humans with anti-Jo-1-positive disease. Collectively, these data suggest that extracellular HARS is homeostatic in normal subjects, and its sequestration contributes to the morbidity of the anti-Jo-1-positive antisynthetase syndrome.

Isolation of monoclonal antibodies from anti-synthetase syndrome patients and affinity maturation by recombination of independent somatic variants.

The autoimmune disease known as Jo-1 positive anti-synthetase syndrome (ASS) is characterized by circulating antibody titers to histidyl-tRNA synthetase (HARS), which may play a role in modulating the non-canonical functions of HARS. Monoclonal antibodies to HARS were isolated by single-cell screening and sequencing from three Jo-1 positive ASS patients and shown to be of high affinity, covering diverse epitope space. The immune response was further characterized by repertoire sequencing from the most productive of the donor samples. In line with previous studies of autoimmune repertoires, these antibodies tended to have long complementarity-determining region H3 sequences with more positive-charged residues than average. Clones of interest were clustered into groups with related sequences, allowing us to observe different somatic mutations in related clones. We postulated that these had found alternate structural solutions for high affinity binding, but that mutations might be transferable between clones to further enhance binding affinity. Transfer of somatic mutations between antibodies within the same clonal group was able to enhance binding affinity in a number of cases, including beneficial transfer of a mutation from a lower affinity clone into one of higher affinity. Affinity enhancement was seen with mutation transfer both between related single-cell clones, and directly from related repertoire sequences. To our knowledge, this is the first demonstration of somatic hypermutation transfer from repertoire sequences to further mature in vivo derived antibodies, and represents an additional tool to aid in affinity maturation for the development of antibodies.

Serological risk factors for concomitant interstitial lung disease in patients with idiopathic inflammatory myopathy.

Interstitial lung disease (ILD) is an extramuscular manifestation associated with increased mortality in idiopathic inflammatory myopathy (IIM). To identify risk factors for ILD in patients with IIM, this study retrospectively enrolled 117 eligible patients from a university medical center. After a comprehensive chart review, 56 patients were stratified into ILD (n = 28) and non-ILD (n = 28) groups. Clinical features, laboratory data, concomitant diseases, and serology profiles were compared. Patients with ILD had high prevalence of anti-Jo1 antibodies (p = 0.002), anti-Ro52 antibodies (p < 0.001), both anti-Jo1 and anti-Ro52 antibodies (p = 0.008), anti-Jo1 or anti-Ro52 antibodies (p < 0.001), and lower initial creatine kinase (CK) levels (p = 0.006). Moreover, patients with anti-Ro52 antibodies and either anti-Ro52 or anti-Jo1 antibodies had 9.17-fold (95% confidence interval [CI]: 2.858-33.487, p < 0.001) and 13.44-fold (95% CI: 4.008-52.757, p < 0.001) increased odds of developing ILD, respectively. By contrast, patients with higher CK levels had 0.99-fold (95% CI: 0.999-0.999, p = 0.011) increased odds of developing ILD. Both anti-Ro52 and anti-Jo1 antibodies were independent serological risk factors for IIM-associated ILD. Because these serology tests are commonly available, they can be used to guide pulmonary screening for patients with IIM to increase neurologist proactivity in recognizing and treating extramuscular conditions.

Proinflammatory Histidyl-Transfer RNA Synthetase-Specific CD4+ T Cells in the Blood and Lungs of Patients With Idiopathic Inflammatory Myopathies.

OBJECTIVE: Autoantibodies targeting histidyl-transfer RNA synthetase (HisRS; anti-Jo-1) are common in the idiopathic inflammatory myopathies (IIMs) and antisynthetase syndrome. This study was undertaken to investigate immunity against HisRS in the blood and lungs of patients with IIM/antisynthetase syndrome. METHODS: Bronchoalveolar lavage (BAL) fluid, BAL fluid cells, and peripheral blood mononuclear cells (PBMCs) from patients with IIM/antisynthetase syndrome (n = 24) were stimulated with full-length HisRS protein or a HisRS-derived peptide (HisRS11-23 ). BAL fluid and PBMCs from patients with sarcoidosis (n = 7) and healthy subjects (n = 12) were included as controls. The CD4+ T cell response was determined according to levels of CD40L up-regulation and cytokine expression using flow cytometry. Anti-Jo-1 autoantibody responses in the serum and BAL fluid were assessed by enzyme-linked immunosorbent assay. Lung biopsy samples from patients with IIM/antisynthetase syndrome (n = 14) were investigated by immunohistochemistry. RESULTS: In BAL fluid, CD4+ T cells from 3 of 4 patients with IIM/antisynthetase syndrome responded to stimulation with HisRS protein, as measured by the median fold change in CD40L expresssion in stimulated cells compared to unstimulated cells (median fold change 3.6, interquartile range [IQR] 2.7-14.7), and 2 of 3 patients with IIM/antisynthetase syndrome had the highest responses to HisRS11-23 (median fold change 88, IQR 27-149). In PBMCs, CD4+ T cells from 14 of 18 patients with IIM/antisynthetase syndrome responded to HisRS protein (median fold change 7.38, IQR 2.69-31.86; P < 0.001), whereas a HisRS11-23 response was present in 11 of 14 patients with IIM/antisynthetase syndrome (median fold change 3.4, IQR 1.87-10.9; P < 0.001). In the control group, there was a HisRS11-23 response in 3 of 7 patients with sarcoidosis (median fold change 2.09, IQR 1.45-3.29) and in 5 of 12 healthy controls (median fold change 2, IQR 1.89-2.42). CD4+ T cells from patients with IIM/antisynthetase syndrome displayed a pronounced Th1 phenotype in the BAL fluid when compared to the PBMCs (P < 0.001), producing high amounts of interferon-γ and interleukin-2 following stimulation. Anti-Jo-1 autoantibodies were detected in BAL fluid and germinal center (GC)-like structures were seen in the lung biopsy samples from patients with IIM/antisynthetase syndrome. CONCLUSION: The results of this study demonstrate a pronounced presence of HisRS-reactive CD4+ T cells in PBMCs and BAL fluid cells from patients with IIM/antisynthetase syndrome as compared to patients with sarcoidosis and healthy controls. These findings, combined with the presence of anti-Jo-1 autoantibodies in BAL fluid and GC-like structures in the lungs, suggest that immune activation against HisRS might take place within the lungs of patients with IIM/antisynthetase syndrome.

Coexistencia de anticuerpos anti-histidil-tRNA-sintetasa y anti-partícula de reconocimiento de la señal en un paciente con polimiositis / Coexistence of anti-Jo1 and anti-signal recognition particle antibodies in a polymyositis patient

Las miopatías inflamatorias idiopáticas son un grupo heterogéneo de miopatías potencialmente tratables. Se clasifican en 4 subtipos: dermatomiositis, polimiositis, miositis autoinmune necrosante y miositis por cuerpos de inclusión, en función de las características clínicas e histológicas. Los anticuerpos asociados a miositis y los autoanticuerpos específicos de miositis se encuentran frecuentemente en pacientes con miopatías inflamatorias, siendo útiles en el diagnóstico y clasificación. El anticuerpo anti-histidil tRNA sintetasa es el más prevalente y el más específico para polimiositis. El anticuerpo de partícula de reconocimiento de señal es también un autoanticuerpo especıfico para polimiositis, pero más infrecuente, y raramente se encuentra en pacientes que presentan otros autoanticuerpos específicos para miositis. En este trabajo se presenta un paciente con polimiositis en el que coexisten los 2 autoanticuerpos en el suero, lo que se considera una situación clínica extremadamente rara. Aquí analizamos la evolución clínica y hallazgos para examinar el efecto de la coexistencia y la posible interacción sobre el pronóstico

Idiopathic inflammatory myopathies are a heterogeneous group of potentially treatable myopathies. They are classified, on the basis of clinical and histopathological features, into four subtypes: dermatomyositis, polymyositis, necrotizing autoimmune myositis and inclusion-body myositis. Myositis-associated antibodies and myositis-specific autoantibodies are frequently found in patients with idiopathic inflammatory myopathies, and are useful in the diagnosis and classification. Anti-histidyl transfer RNA synthetase antibody is the most widely prevalent and is highly specific for polymyositis. Signal recognition particle antibody is also a specific autoantibody for polymyositis, but it is infrequent and rarely found in patients having other myositis-specific autoantibodies. We present a man with polymyositis who had both antibodies in serum, which is considered an extremely rare clinical situation. Here we analyze the clinical course and findings, and examine the effect of the coexistence and possible interaction on prognosis

Mass cytometry reveals an impairment of B cell homeostasis in anti-synthetase syndrome.

Recent data suggest the implication of T, B and NK cells in the anti-synthetase syndrome (ASyS); nevertheless their role and activation states are poorly described. We performed deep immune-profiling using 37 markers on peripheral blood cells from 10 ASyS patients versus 17 healthy donors (HD) and 26 myositis control patients. We show decreased percentages of memory B cells in ASyS patients (mean ±â€¯SEM: ASyS = 13 ±â€¯3%, HD = 37 ±â€¯4% and 'myositis controls' = 32 ±â€¯3), counterbalanced by increased percentages of naïve B cells. Interestingly, perifascicular infiltrations of memory B cells within muscle biopsies of ASyS patients suggest that they niche within the muscle.

Screening for Myositis Antibodies in Idiopathic Interstitial Lung Disease.

PURPOSE: International guidelines recommend screening for connective tissue disease (CTD) with autoantibodies when evaluating patients with idiopathic interstitial lung disease (ILD). Idiopathic inflammatory myositis comprises of a subgroup of CTD diagnosed with myositis antibodies (MA), often presenting with ILD. Our aim was to evaluate the utility of MA screening in patients with idiopathic ILD. METHODS: A retrospective analysis was conducted on patients referred with idiopathic ILD to a tertiary centre ILD clinic who were screened for MA. Patients with known or suspected CTD were excluded. Descriptive statistics, univariate analysis and multivariable logistic regression were used to detect associations between MA and patient characteristics. RESULTS: Of 360 patients, 165 met inclusion criteria and 44 (26.7%) were identified to have MA. Fourteen patients (8.5%) had a change in diagnosis as a result of MA screening. Multivariable logistic regression identified the presence of MA to be associated with current smoking [OR 6.87 (1.65-28.64), p = 0.008] and a diffusing capacity of < 70% predicted [OR 2.55 (1.09-5.97), p = 0.03]. In patients with a change in diagnosis due to MA screening, 3 (1.8%) underwent a surgical lung biopsy and 2 (1.2%) were previously treated with antifibrotic therapy. CONCLUSIONS: Screening for MA in patients with idiopathic ILD can contribute to a change in patient diagnosis, and may prevent invasive testing and unproven use of antifibrotic therapy. These results support the addition of MA to CTD screening panels during the initial evaluation of idiopathic ILD.

Mechanics hands in patients with antisynthetase syndrome: 25 cases.

BACKGROUND: Antisynthetase antibodies (ASA) are directed against aminoacyl-tRNA-synthetases, ubiquitous enzymes of which eight types have hitherto been described. They are seen primarily in antisynthetase syndrome (ASS), in which diffuse interstitial lung disease is associated with inflammatory myopathy, joint involvement and cutaneous signs, in particular mechanic's hands. The aim of this study was to determine the prevalence and semiological characteristics of cutaneous involvement in patients presenting ASA. PATIENTS AND METHODS: We carried out a retrospective study of the medical files of patients with ASA diagnosed at the Strasbourg University Hospital between 1994 and 2009. RESULTS: We identified 22 women and 3 men presenting ASS (n=21), dermatomyositis (n=3) or sclerodermatomyositis (n=1). Mean age at the time of diagnosis was 56 years (12-79). The most commonly seen antibodies were anti-Jo1 (n=19), with the other cases of ASA involving anti-PL12 (n=3), anti-PL7 (n=2) and anti-EJ (n=1) antibodies. Five patients died from pulmonary complications. Mechanic's hands (characteristic plaques and papules along the edge of the first fingers on both hands) were found in 10 patients with ASS (7 cases) or dermatomyositis (3 cases), at the time of diagnosis in 7 cases and during a systemic episode in 3 cases. Muscular involvement was seen in all patients: 9 had diffuse interstitial lung disease and 8 had joint involvement. Cutaneous signs regressed totally or partially in all patients under treatment; in 6 patients, worsening was seen during systemic episodes of the disease. One of the 10 patients died through pulmonary complications. DISCUSSION: Mechanic's hands are a key indicator in cases of ASA and its outcome is intimately linked with underlying systemic involvement, particularly pulmonary. The characteristic semiology enables this disorder to be recognised and allows differentiation from psoriasis or irritant contact dermatitis of the hands, and it does not vary according to antibody. Whether or not the disease is life-threatening is unaffected by the presence of this sign.

Myositis-specific autoantibodies in Japanese patients with juvenile idiopathic inflammatory myopathies.

OBJECTIVES: The aim of our study is to clarify the association of myositis-specific autoantibodies (MSAs) with clinical and laboratory features in Japanese patients with juvenile idiopathic inflammatory myopathies (JIIMs). METHODS: We retrospectively analyzed the frequency of MSAs and their association with clinical or laboratory findings in 25 Japanese patients with JIIMs in Hokkaido district. RESULTS: Eighteen of the 25 patients (72%) were positive for MSAs; seven with anti-melanoma differentiation associated gene (MDA) 5 (28%), five with anti-transcriptional intermediary factor (TIF)-1γ (20%), four with anti-MJ/nuclear matrix protein (NXP)-2 (16%), two with anti-Jo-1 (8%), one with anti- HMG-CoA reductase, one with anti-signal recognition peptide (SRP) antibodies (4% each), including co-existence and transition of MSAs in one patient each. Anti-MDA5 antibodies were related to interstitial lung disease (ILD) and arthritis but not to amyopathic juvenile dermatomyositis. Drug-free remission was achieved, once ILD was overcome in this group. Anti-TIF-1γ antibodies were associated with typical rashes and mild myositis. Anti-MJ/NXP2 and anti-SRP antibodies were associated with severe muscle weakness. No patient was complicated with malignancy. CONCLUSION: Anti-MDA5 antibodies are prevalent and closely associated with ILD in our series compared with other countries. There was no apparent difference in clinical features associated with other MSAs among races.

Coexistence of anti-Jo1 and anti-signal recognition particle antibodies in a polymyositis patient. / Coexistencia de anticuerpos anti-histidil-tRNA-sintetasa y anti-partícula de reconocimiento de la señal en un paciente con polimiositis.

Idiopathic inflammatory myopathies are a heterogeneous group of potentially treatable myopathies. They are classified, on the basis of clinical and histopathological features, into four subtypes: dermatomyositis, polymyositis, necrotizing autoimmune myositis and inclusion-body myositis. Myositis-associated antibodies and myositis-specific autoantibodies are frequently found in patients with idiopathic inflammatory myopathies, and are useful in the diagnosis and classification. Anti-histidyl transfer RNA synthetase antibody is the most widely prevalent and is highly specific for polymyositis. Signal recognition particle antibody is also a specific autoantibody for polymyositis, but it is infrequent and rarely found in patients having other myositis-specific autoantibodies. We present a man with polymyositis who had both antibodies in serum, which is considered an extremely rare clinical situation. Here we analyze the clinical course and findings, and examine the effect of the coexistence and possible interaction on prognosis.

Serum levels of B-cell activating factor of the TNF family (BAFF) correlate with anti-Jo-1 autoantibodies levels and disease activity in patients with anti-Jo-1positive polymyositis and dermatomyositis.

BACKGROUND: B-cell activating factor of the tumour necrosis factor family (BAFF) plays a role in autoantibody production and is elevated in dermatomyositis (DM) and anti-Jo-1-positive polymyositis (PM). We investigated the inter-relationships between serum levels of BAFF, anti-Jo-1 autoantibodies, and disease activity. METHODS: Serum levels of BAFF and anti-Jo-1 antibodies measured by enzyme-linked immunosorbent assay (ELISA) were compared to levels of myoglobin, creatine kinase (CK), aminotransferases (alanine (ALT) and aspartate (AST)), C-reactive protein (CRP), and disease activity assessed by the Myositis Disease Activity Assessment Tool in 63 anti-Jo-1 antibody-positive DM/PM patients. Serial serum samples collected at 2 (46 cases) and 3-5 time points (23 cases) were included. Relationships between BAFF, anti-Jo-1, disease activity, CRP, and their longitudinal changes were evaluated using correlation analysis, multiple regression (MR), path analysis (PA), and hierarchical linear models (HLM). RESULTS: Cross-sectional assessment demonstrated significant correlations between the levels of BAFF and anti-Jo-1 antibodies which were associated with levels of CK, myoglobin, AST, and CRP, as well as multivariate associations between BAFF, anti-Jo-1 antibodies, and CK levels. PA revealed direct effects of anti-Jo-1 antibodies on CK (ß = 0.41) and both direct (ß = 0.42) and indirect (through anti-Jo-1 antibodies; ß = 0.17) effects of BAFF on CK. Changes in levels of both BAFF and anti-Jo-1 between two time points (Δ) were associated with Δmyoglobin and Δaminotransferases and changes of BAFF correlated with ΔCK, Δcutaneous, Δmuscle, Δglobal, and Δskeletal disease activities. The longitudinal analysis showed a high intra-individual variability of serum levels of BAFF over time (97%) which could predict 79% of the variance in anti-Jo-1 levels. The anti-Jo-1 variability was explained by inter-individual differences (68%). The close longitudinal relationship between levels of BAFF, anti-Jo-1, and disease activity was supported by high proportions of their variance explained with serum levels of CK and CRP or pulmonary and muscle activities. CONCLUSION: Our findings of associations between levels of BAFF and anti-Jo-1 antibodies in serum and myositis activity suggest a role of this cytokine in disease-specific autoantibody production as part of disease mechanisms, and support BAFF as a potential target for intervention in anti-Jo-1-positive myositis patients.

Immunopathogenesis of the Anti-Synthetase Syndrome.

Among the inflammatory myopathies, anti-tRNA-synthetase syndrome (ASyS) is a severe autoimmune condition characterized by extramuscular involvement, affecting especially the lungs. ASyS specific serological markers are anti-tRNA-synthetase autoantibodies, among which anti-histidyl-tRNA-synthetase is the most common. In the past decades, ASyS has been distinguished by unique histological features attributed to a specific pathogenesis. Research has highlighted the role of environmental factors and infections as possible triggers. Tissue modifications of histidyl-tRNA-synthetase (HisRS) expression might be responsible for the recruitment and activation of both innate and adaptive immune cells. HisRS not only acts through antigenic properties, but also through many others, including chemoattraction, innate pathway activation, and cytokine-like functions. Favored by a certain genetic background, this whole activation of immunity results in widespread and specific tissue damage and finally leads to visible heterogeneous symptoms characterizing the disease state. Understanding the pathogenesis of ASyS is essential to improving patient care by identifying biomarkers and designing new therapeutic strategies accordingly. Therefore, this review details the recent hypotheses concerning the dynamic of ASyS pathogenesis with the aim of enlightening the development of new therapeutic axes in the future.

An effective algorithm for the serological diagnosis of idiopathic inflammatory myopathies: The key role of anti-Ro52 antibodies.

BACKGROUND: Patients with suspected idiopathic inflammatory myopathies (IIM) are commonly tested for the presence of anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) on HEp-2 cell substrates. However, ANA-IIF false negative tests may occur in IIM because some antigens, such as Jo1 and Ro52, may be scarcely expressed on HEp-2 cells. In addition, cytoplasmic staining is often not appropriately investigated by a specific antibody assay, leading to decreased clinical sensitivity of the ANA test. We evaluated the diagnostic impact of different strategies using different combination of myositis-related autoantibody tests. METHODS: Sera from 51 patients with an established diagnosis of IIM were tested for ANA by IIF on HEp-2 cells and for myositis-specific antibodies (MSA) and myositis-associated antibodies (MAA) by lineblot methods. RESULTS: Forty-four/51 (86.3%) samples tested positive with at least one of the three methods and seven were negative with all methods. Of the 44 positive samples, 9 (20.5%) tested negative for the ANA-IIF test and positive for MAA/MSA. Anti-Ro52 were the most prevalent autoantibodies in IIM patients (21/51; 41%), frequently associated with anti-Jo1 antibodies (13/21; 62%). 13 (16%) anti-Ro52 and anti-Jo1 negative samples were reactive to MSA. CONCLUSIONS: Our findings suggest that when IIM is clinically suspected, the optimal diagnostic algorithm is to associate the ANA-IIF screening test with a specific test for anti-Ro52 and anti-Jo1 antibodies. Should all these tests be negative, serological tests for MSA are recommended.

Clinical spectrum of anti-Jo-1-associated disease.

PURPOSE OF REVIEW: To provide the most recent evidence on anti-Jo-1 syndrome. RECENT FINDINGS: Several new evidences on anti-Jo-1 syndrome have recently emerged. It has been clearly established that, at disease onset, the classic clinical triad (arthritis, myositis and interstitial lung disease - ILD) is only rarely observed. Indeed, disease onset with an isolated arthritis is common. Patients presenting with an isolated manifestation are at high risk for the subsequent occurrence of initially lacking triad findings. Moreover, the ex-novo occurrence of accompanying features such as Raynaud's phenomenon, mechanic's hands and fever during follow-up is a strong risk factor for the occurrence of overt antisynthetase syndrome (ASSD) with further triad manifestations. Several contributions on ILD involvement and prognosis have been published, as well as the distinctive muscle MRI characteristics compared with healthy controls, and a novel definition of a rare skin manifestation (hiker's feet). SUMMARY: Recent evidence has shed a light on the need for a better understanding of the clinical course, imaging modalities and prognosis of anti-Jo-1 syndrome, providing some relevant elements to allow early diagnosis of this often unrecognized disease.

Autoantibodies in children with juvenile dermatomyositis: A single centre experience from North-West India.

The objective of this study is to determine autoantibody profile in children with juvenile dermatomyositis (JDM). Children who were diagnosed with JDM (either recently diagnosed during the study period or follow-up patients) were included in the study. Autoantibodies were detected with commercially available Immunodot kit. Thirty patients were included in the study. Nine out of thirty patients (30%) were positive for one of the 12 autoantibodies tested. Anti-SRP antibody was most common antibody detected in 3 patients followed by anti-MDA-5 antibody in 2 patients; while anti-Jo1 antibody, anti-TIF1-γ antibody, anti-Mi-2 antibody, and anti-PM-Scl antibody were positive in 1 patient each. A different disease phenotype was observed with each autoantibody. The patient with anti-Jo1 antibody had a severe systemic disease in the form of interstitial lung disease; patients with anti-MDA-5 antibody and anti-Mi2 antibody had more severe skin disease with mild muscle disease and patients with anti-SRP antibody had significant skin and muscle disease. Anti-TIF1-γ and anti-PM-Scl antibodies were seen in patients with features of overlap syndrome (myositis-scleroderma). Estimation of autoantibodies may serve as an adjunct tool in delineating and defining distinct clinical phenotypes in children diagnosed with juvenile dermatomyositis. They may also help in prognostication.

Serum Jo-1 Autoantibody and Isolated Arthritis in the Antisynthetase Syndrome: Review of the Literature and Report of the Experience of AENEAS Collaborative Group.

Anti-Jo-1 is the most frequently detectable antibody in the antisynthetase syndrome (ASSD), an autoimmune disease characterized by the occurrence of arthritis, myositis, and interstitial lung disease (ILD). Recently, we organized an international collaborative group called American and European NEtwork of Antisynthetase Syndrome (AENEAS) for the study of this rare and fascinating disease. The group collected and published one of the largest series of ASSD patients ever described and with one of the longer follow-up ever reported. The number of participating centers is steadily increasing, as well as the available cohort. In the first paper, we showed that arthritis, myositis, and ILD may be frequently the only feature at disease onset, raising problems to reach a correct diagnosis of this syndrome. Nevertheless, we first observed that the ex novo appearance of further manifestations is common during the follow-up, strengthening the importance of a correct diagnosis. In our cohort, the 24 % of the 243 patients up to now collected had isolated arthritis as a presenting feature. These patients represent the most intriguing group in terms of differential diagnosis and clinical time course. Furthermore, data on this aspect are scanty, the reason that lead us to evaluate these aspects in our cohort of patients, reviewing also available literature. In fact, the most relevant aspect is that ASSD is rarely suspected in this setting of patients, in particular in case of poliarticular involvement, positive rheumatoid factor (RF), or anti-cyclic citrullinated peptide antibodies (ACPA) or evidence of joint erosions at plain radiographs. These findings were not rare in our cohort, and they have been also described in other series. Furthermore, manifestations such as Raynaud's phenomenon, mechanic's hands, and fever that may lead to the suspect of ASSD are observed only in a third of cases. If we consider the high rate of clinical picture progression in these patients, we feel that ASSD should be carefully considered in all patients presenting with isolated arthritis, even in those with erosive, RF, and ACPA-positive arthritis.

Organizing pneumonia as the first manifestation of anti-synthetase syndrome.

BACKGROUND: Anti-synthetase syndrome associated interstitial lung disease can occur either simultaneously, before, or after the development of polymyositis/dermatomyositis. Histology of interstitial lung disease can be nonspecific interstitial pneumonia, usual interstitial pneumonia, diffuse alveolar damage, organizing pneumonia. Organizing pneumonia associated anti-synthetase syndrome is a rare finding especially as the first manifestation. CASE PRESENTATION: We report a 41 year old male patient who presented with organizing pneumonia and 2 years following the onset, developed polymyositis with anti-JO-1 antibody positivity. CONCLUSION: It is important to screen patients with organizing pneumonia for anti-synthetase syndrome which can be manifested later.