Idiopathic Inflammatory Myopathies—Treatment Perspective of Highly Specialised Rheumatology Centre

Background/Objectives: Idiopathic inflammatory myopathies (IIMs) are chronic immune-mediated disorders, causing striated muscle weakness and extramuscular symptoms. Real-world, single-centre data are needed to interpret phenotype patterns and evolving therapies. Methods: A single-centre, retrospective cohort study was conducted at the Rheumatology Clinic of the National Institute of Geriatrics, Rheumatology and Rehabilitation, Warsaw, Poland from 1 January 2022 to 31 December 2025. Data included demographics, IIM subtypes, extramuscular involvement, co-existing Sjögren disease (SD), biopsy results, autoantibodies, and treatment. Due to sample size, descriptive analysis was used. Results: The study included 35 patients (31.4% men). Mean age was 50.7 years; mean body mass index (BMI) was 26.0 kg/m2. The cohort consisted of 10 dermatomyositis (DM), one polymyositis (PM), two immune-mediated necrotising myopathy (IMNM), one inclusion body myositis (IBM), 16 anti-synthetase syndrome (ASyS), four juvenile dermatomyositis (JDM), and one clinically amyopathic dermatomyositis (CADM). SD co-occurred in eight cases, including six cases of ASyS. Anti-Jo1 was observed in 13 ASyS cases and one DM. Glucocorticoids (GCSs) were administered in all patients for induction in addition to cyclophosphamide (28.6%), mycophenolate mofetil (MMF) (51.4%), and methotrexate (MTX) (17.1%). Maintenance therapy included MTX (20%), MMF (31.4%), rituximab (34.3%), azathioprine (AZA) (42.9%), and others. Two DM, two JDM, and one ASyS patient received JAK inhibitors, one DM and one JDM anifrolumab, one IBM sirolimus, and four patients with interstitial lung disease (ILD) nintedanib. Conclusions: This Polish single-centre cohort shows effective use of novel therapies for IIM. Sirolimus, JAK inhibitors, and nintedanib were effective. Co-occurrence of SD in ASyS patients requires further research.