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.