The clinical phenotype of patients positive for antibodies to myositis and myositis-related disorders

Inflammatory myopathies are a clinically diverse group of diseases, in which the detection of particular autoantibodies may facilitate diagnosis, treatment, and prognosis. The aim of this report is to summarize our experience with specific autoantibody testing in patients with inflammatory myopathies. Data were collected over the last decade in the Autoimmune Center of the Sheba Medical Center, a tertiary referral hospital. Data regarding patients' positive for autoantibodies against Jo-1, PL-7, PL-12, SRP, Mi-2, Ku, and PM-Scl antigens were retrospectively collected. Patient demographics, clinical characteristics, and mortality were recorded. Descriptive statistics (mean, standard deviation, frequency, and percentage) were calculated. A total of 507 patients were surveyed for sclero-poly-synthetase antibodies, as part of the diagnostic workup of myositis/myalgia or interstitial lung disease. Forty-three patients were found positive for one or more of the abovementioned antibodies, and 23 of them (53.49%) had interstitial lung disease (ILD). Four patients were positive for anti-PL-7, three of them had ILD and Raynaud's phenomenon. Five patients were positive for anti-Ku, and four of them had both arthritis and Raynaud's phenomenon. Nine patients were positive for anti-Mi-2, and six of them were given diagnosed with dermatomyositis. Ten patients were positive for anti-SRP, and six of them had cancers of various types. Our results reiterate the previously recognized associations between anti-Mi-2 and dermatomyositis, anti-Ku and Raynaud's phenomenon, and between anti-PL-7 and ILD. In addition, our data support an association between anti-SRP autoantibody positivity and malignancy, which calls for further investigation.