Discussion
Antisynthetase syndrome is a multi-organ syndrome causing myositis, which manifests as symmetric (85%) proximal (60%) weakness, acute pain (34%-50%), progressing to muscle atrophy and fibrosis in 66%.3 Weakness of cricopharyngeus and hypopharynx can lead to dysphagia 15-40% of the time.1 Spirometry can reveal weakness in the diaphragm or the intercostal muscles.1
ARS antibodies are detected in 25-35% of patients with idiopathic inflammatory myopathy. Myopathy is detected by electrodiagnostic or laboratory evidence in the non-Jo-1 groups.1,5Steroid-responsive myopathy is usually a late manifestation of the disease course (17 months), however here it occurred on presentation.1,5
Labs reveal elevated muscle enzymes, positive ANA, antisynthetase antibodies, and elevated acute-phase reactants.1Electromyography shows myopathy, but up to 15% of tests are normal.1 Muscle MRI shows edema not limited to compartment or myotome.6
Muscle biopsy shows perimysial macrophages and lymphocytes, degenerating muscle fibers and regenerating muscle fibers, muscle fiber necrosis and perifascicular atrophy similar to dermatomyositis, but without vascular changes.1 EJ-antibodies produce a cytoplasmic pattern on immunofluorescence.1
Corticosteroids produce an incomplete response.4 Long term immunosuppressant medications, such as Rituximab, Cyclophosphamide, IVIG, or Methotrexate are required 80% of the time.475% of patients respond to Rituximab at 375 mg/M2every 10 to 12 weeks.1
It is important to consider antisynthetase syndrome in the differential diagnosis of weakness and signs of mult-organ disease, often diagnosed as multiple diseases. Successfully diagnosing antisynthetase syndrome results in better patient outcomes.