Background/Purpose: In clinical practice, immunoblot assays are being used more frequently as a diagnostic tool for systemic autoimmune rheumatic diseases (SARDs).Our aim was to evaluate the significance that an extended analysis of scleroderma/myositis-related autoantibodies (aAbs) detected by immunoblot contributes to the diagnosis of SARDs patients.

Methods: From November 2017 to November 2023, we examined all medical records of patients at our center who had positive immunoblot results related to scleroderma or myositis (Euroimmune AG, Lübeck, Germany). The high suspicion of SARDs in patients with nonspecific symptoms led to the request of these assays.

Results: 410 patients (127 men/283 women; mean age 58.21 ± 16.29 years) were positive for at least 1 aAb, 69 of them were positive for 2 aAbs.  Main clinical features at the time of immunoblot requests were: arthralgia/arthritis (n=192), Raynaud’s phenomenon (n=165), rash (n=64), myopathy (n=56) and sicca syndrome (n=50). During follow-up, 82 patients were diagnosed with overlap myositis, 75 with scleroderma, 52 with other inflammatory diseases, 41 with interstitial pneumonia with autoimmune features (IPAF), 36 with undifferentiated connective tissue disease (UCTD), 20 with Sjögren’s syndrome, 18 with dermatomyositis, 17 with systemic lupus erythematosus and finally 1 with necrotizing myositis.  In 68 patients the diagnosis of SARD was finally ruled out (Figure 1). Interstitial lung disease (ILD) was present in 133 patients, being particularly frequent in those with anti-PL12 (p=0.017) in comparison to the rest of the specificities. Cancer was detected in 35 (8.53%) patients, 20 of them were anti-Ro52+ (p=0.01) (Table 1).

Conclusion: For patients with a high clinical suspicion of SARDs, immunoblot assays are very helpful in the diagnosis process.  While some aAbs, such as anti-Mi2 and anti-Th/To, remain to be nonspecific, other Abs including anti-PL12 and anti-Ro52 are particularly helpful in detecting SARDs patients with associated ILD and cancer, respectively.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/role-of-scleroderma-myositis-related-autoantibodies-detected-by-immunoblot-to-the-diagnosis-of-systemic-autoimmune-rheumatic-diseases-in-410-patients-from-a-single-referral-center/