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.

Clinical Spectrum Time Course in Anti Jo-1 Positive Antisynthetase Syndrome: Results From an International Retrospective Multicenter Study.

Anti Jo-1 antibodies are the main markers of the antisynthetase syndrome (ASSD), an autoimmune disease clinically characterized by the occurrence of arthritis, myositis, and interstitial lung disease (ILD). These manifestations usually co-occur (for practical purpose complete forms) in the same patient, but cases with only 1 or 2 of these findings (for practical purpose incomplete forms) have been described. In incomplete forms, the ex novo occurrence of further manifestations is possible, although with frequencies and timing not still defined. The aim of this international, multicenter, retrospective study was to characterize the clinical time course of anti Jo-1 positive ASSD in a large cohort of patients. Included patients should be anti Jo-1 positive and with at least 1 feature between arthritis, myositis, and ILD. We evaluated the differences between complete and incomplete forms, timing of clinical picture appearance and analyzed factors predicting the appearance of further manifestations in incomplete ASSD. Finally, we collected 225 patients (58 males and 167 females) with a median follow-up of 80 months. At the onset, complete ASSD were 44 and incomplete 181. Patients with incomplete ASSD had frequently only 1 of the classic triad findings (110 cases), in particular, isolated arthritis in 54 cases, isolated myositis in 28 cases, and isolated ILD in 28 cases. At the end of follow-up, complete ASSD were 113, incomplete 112. Only 5 patients had an isolated arthritis, only 5 an isolated myositis, and 15 an isolated ILD. During the follow-up, 108 patients with incomplete forms developed further manifestations. Single main feature onset was the main risk factor for the ex novo appearance of further manifestation. ILD was the prevalent ex novo manifestation (74 cases). In conclusion, ASSD is a condition that should be carefully considered in all patients presenting with arthritis, myositis, and ILD, even when isolated. The ex novo appearance of further manifestations in patients with incomplete forms is common, thus indicating the need for an adequate clinical and instrumental follow-up. Furthermore, the study clearly suggested that in ASSD multidisciplinary approach involving Rheumatology, Neurology, Pneumology, and Internal Medicine specialists is mandatory.