gms | German Medical Science

Introduction: Antisynthetase syndrome is a polymyositis characterized by accompanying interstitial lung disease (ILD), Raynaud’s phenomenon, and arthritis. Antibodies against aminoacyl-t-RNA synthetase are considered disease specific and solitary [1]. ELISA blotted myositis specific antibodies define entities of inflammatory myositis correlated to clinical features [2]. To our knowledge, there are no reports of seroconversions in myositis patients during their course of disease.

Methods: We report on two patients, presented to our rheumatology department between 2020 and 2023. Patient data were analysed retrospectively, all patients underwent lung high resolution computed tomography (HRCT), Magnet resonance imaging (MRI) of the concerned muscles as well as bronchoscopy with lavage. In addition, serological diagnostic procedure were completed by applying specific ELISA myositis blotting system (Euroimmun).

Results: Both patients presented with respiratory insufficiency, myasthenia and arthritis. Both patients under DMARD therapy. Pat.1 (female, 36 years) showed beyond anti-Jo-1 antibody ANA 1:640, RF+, and Ro-52 antibodies, whereas Mi-2 was negative. Evidence of ILD and highly inflammatory myositis (elevated serum CK and myoglobin, MRI) were treated by 1g rituximab+15 mg MTX sc., after treatment failure followed by 5x courses cyclophosphamide (750 mg/m²). Due to treatment refractory situation 7 cycles of plasmapharese and high-dose immunoglobulins were administrated. Subsequently highly positive initial detection of a Mi-2a antibody in addition to the above-mentioned serum findings (fig.1 [Fig. 1]). Pat.2 (female, 64 years) showed with ANA 1:1280 and NXP2 anti-bodies in addition to Jo-1 (however, without Mi-2a). ILD, florid myositis (CK, MRI), and rapid disease progression under 6 courses of cyclophosphamide 750 mg/m² required 7 courses of plasmapharese followed by 1 g Rituximab, later on with 2 g MMF ad on. In addition, increased liver enzymes under leflunomide and allergy to rituximab complicated cinical course. The patient seroconverted from Mi-2a negative to positive in addition to the above-mentioned findings (fig.1 [Fig. 1]). Neither patient showed any skin changes specific to dermatomyositis.

Conclusion: Both patients represented treatment refractory disease of Jo-1 antisynthetase syndrome on intensive treatment courses accompanied by an extension of autoimmune serology by Mi-2a in Jo-1 positive myositis. In what way the uncommon Mi-2a serum positivity in Jo-1 positive patients reflects the therapy refractory situation in both patients remains to be unclear.