LAUSR

Immunoblot assays are increasingly used in clinical practice as part of the diagnostic armamentarium of systemic autoimmune rheumatic diseases (SARDs).To assess the contribution of an extended scleroderma/myositis-related antibodies (Ab) determination by immunoblot to the diagnosis of patients with SARDs.We reviewed all medical records of patients with positive scleroderma/myositis-related Ab line blot determinations (Euroimmune AG, Lübeck, Germany) in our center from November 2017 to September 2020. These assays were requested due to high suspicion of SARDs in patients presenting with non-specific symptoms.134 patients (37men/97women; mean age 59.6 ± 14.8 years) were positive for at least 1 Ab, 25 of them were positive for 2 Abs. Main clinical features at the time of immunoblot requests were: arthralgia/arthritis (n=88), Raynaud’s phenomenon (n=59), rash (n=27), sicca syndrome (n=14.9%), myopathy (n=18). During follow-up, 28 patients were diagnosed with undifferentiated connective tissue disease (UCTD), 26 scleroderma, 23 overlap myositis, 18 interstitial pneumonia with autoimmune features (IPAF), 8 other inflammatory diseases, 8 Sjögren’s syndrome, 7 systemic lupus erythematosus, 5 dermatomyositis, 1 necrotizing myositis. In 10 patients the diagnosis of SARD was finally ruled out (Figure 1). Interstitial lung disease (ILD) was present in 50 patients, being particularly frequent in those with anti-PL12, anti-PL7 and anti-MDA5 Abs. Cancer was detected in 9 (6.7%) patients, 6 of them were anti-Ro52 + (Table 1).Immunoblot assays are of great help in the diagnosis of patients with high clinical suspicion of SARDs. While some Abs, such as anti-Ro52, anti-Ku and anti-PMScl75/100, remain to be nonspecific, other Abs including anti-PL12, anti-PL7 or anti-MDA5 are particularly helpful in detecting SARDs patients with associated ILD.Table 1.Mi-2 (n=5)PL-7(n=6)PL-12(n=4)Jo-1(n=6)MDA5(n=1)antiRo52(n=57)SRP (n=3)Scl-70(n=12)CENP(n=14)Th(n=2)Ku(n=14)Fibrilarina (n=2)PM-Scl75/100 (n=23)NOR90(n=8)RNA pol(n=2)ILD04 (66.7)4 (100)3 (50)1 (100)19 (33.3)07 (58.3)1 (7.1)07 (50)1 (50)9 (39.1)5 (62.5)0Cancer1 (20)00006 (10.5)1 (33.3)0001 (7.1)0000None declared