Antisynthetase syndrome
Antisynthetase syndrome is an autoimmune overlap disorder defined by an antiaminoacyl-tRNA synthetase antibody, most often anti-Jo-1, together with interstitial lung disease, myositis, non-erosive arthritis, Raynaud phenomenon, mechanic's hands, and fever. Interstitial lung disease, not the myositis, drives morbidity and mortality and can precede or occur without muscle disease. Treatment starts with high-dose glucocorticoids plus a lung-directed steroid-sparing agent such as mycophenolate mofetil or azathioprine, escalating to rituximab or cyclophosphamide for rapidly progressive lung disease.
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What this article covers
- Overview
Definition: antisynthetase syndrome is an autoimmune overlap disorder defined by an antibody against an aminoacyl-transfer RNA (tRNA) synthetase, most commonly anti-Jo-1, together with a…
- Epidemiology
Frequency within idiopathic inflammatory myopathy: antisynthetase syndrome occurs in approximately 30% of patients with dermatomyositis or polymyositis.
- Risk factors
Underlying dermatomyositis or polymyositis: antisynthetase syndrome develops within an existing or evolving myopathy rather than as an isolated primary process.
- Pathophysiology
Antibody target: aminoacyl-tRNA synthetases are cytoplasmic enzymes that charge transfer RNA with its matching amino acid during protein translation; anti-Jo-1 targets histidyl-tRNA synthetase specifically.
- Clinical features
Interstitial lung disease as the dominant and sometimes isolated feature: progressive dyspnea and cough, occasionally severe and rapidly progressive, that can appear before, without, or independently of muscle disease.
- Differential diagnosis
Dermatomyositis without an antisynthetase antibody: classic photosensitive rashes and proximal weakness but a negative antiaminoacyl-tRNA synthetase panel and a lower burden of severe interstitial lung disease (dermatomyositis).
- Diagnosis
The diagnosis is made by the combination of a positive antiaminoacyl-tRNA synthetase antibody, most often anti-Jo-1, and at least one compatible feature, interstitial lung disease, myositis…
- Management
First, start prednisone 1 mg/kg/day PO once daily, up to a maximum of 80 mg/day, maintained for 4 to 6 weeks before a taper of about 10% of the dose every 2 to 4 weeks once creatine kinase normalizes and strength or lung function improves.
- Complications
Progressive pulmonary fibrosis and respiratory failure: the principal driver of morbidity and mortality when lung disease advances despite treatment.
- Prognosis
Anti-Jo-1 antibody positivity predicts worse outcomes, driven by the associated interstitial lung disease rather than by the severity of muscle involvement.
- Prevention
Screen every antibody-positive patient with high-resolution chest computed tomography and pulmonary function testing at diagnosis, and reassess forced vital capacity and diffusing capacity every 3 to 6 months.
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Related articles
- Dermatomyositis
Dermatomyositis is a complement-mediated inflammatory myopathy causing symmetric proximal weakness with pathognomonic skin findings, heliotrope rash and Gottron papules, that separate it from polymyositis. It carries a 3- to 12-fold increased malignancy risk and a distinct interstitial lung disease burden that drive workup and therapy. First-line treatment is high-dose prednisone with an early steroid-sparing agent.
- Polymyositis
Polymyositis is an idiopathic inflammatory myopathy causing symmetric, subacute proximal muscle weakness with no rash, driven by endomysial CD8-positive T-cell invasion of non-necrotic, MHC class I-expressing muscle fibers. It is a diagnosis of exclusion confirmed by muscle biopsy, and first-line treatment is high-dose prednisone with a steroid-sparing agent such as methotrexate or azathioprine started concurrently.
- Interstitial lung disease
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- Raynaud phenomenon
Raynaud phenomenon is episodic digital vasospasm with triphasic pallor, cyanosis, and reactive hyperemia, split into a benign primary form and a secondary form driven by an underlying connective tissue disease. Diagnosis is clinical, with nailfold capillaroscopy and an autoantibody panel screening for systemic sclerosis, and treatment starts with cold avoidance before a dihydropyridine calcium channel blocker such as nifedipine.
- Rheumatoid arthritis
Rheumatoid arthritis is a chronic systemic autoimmune disease causing symmetric small-joint polyarthritis of the hands and feet that spares the distal interphalangeal joints, with morning stiffness over an hour. Diagnosis combines the ACR/EULAR classification criteria with rheumatoid factor, anti-CCP antibody, and radiographs. Treat-to-target management anchors on methotrexate, escalating to a biologic or targeted synthetic disease-modifying antirheumatic drug when remission is not reached.