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anti-synthetase syndrome

Etiology: - dermatomyositis - polymyositis - other autoimmune diseases * not seen in patients with inclusion body myositis [6] Epidemiology: - rare - more prevalent in women than in men Pathology: - autoantibody against tRNA synthetases - anti-Jo1 Ab is most common antibody Clinical manifestations: - interstitial lung disease (may be only manifestation) - dyspnea, respiratory distress - inflammatory myopathy - proximal muscle weakness (hips, shoulders) - difficulty raising head - difficulty standing from sitting - symmetric inflammatory polyarthritis affecting small joints - variable features include - low-grade fever - Raynaud's phenomenon - mechanics hands [3] - disease may be slowly progressive - intermittent relapses may occur Laboratory: - serum creatine kinase is often elevated (as high as 20,000 IU/L [3] - anti-Jo1 Ab in serum may be positive - anti-SSA Ab in serum may be positive - antinuclear antibody may be high titer - always check serum TSH when evaluating myopathy Special laboratory: - electromyography may be abnormal - muscle biopsy may be abnormal - pulmonary function testing may be abnormal - lung biopsy - swallowing study as indicated Radiology: - chest X-ray - high-resolution CT of lungs - characteristic of interstitial lung disease - lower lobe predominantly peripheral ground-glass opacities - subpleural reticulation - traction bronchiectasis - MRI of thorax as indicated Complications: - pulmonary fibrosis - pulmonary hypertension Management: - see specific etiology - glucocorticoids* - other immunosuppressive agents - azathoprine* - methotrexate * prednisone 60 mg PO QD + azathioprine 150 mg PO QD * prednisone alone (NEJM) [7]

General

myositis (inflammatory myopathy) syndrome

References

  1. Wikipiedia: Antisynthetase syndrome https://en.wikipedia.org/wiki/Antisynthetase_syndrome
  2. Christopher-Stine L, Robinson DR, Wu CC, Mark EJ. Case records of the Massachusetts General Hospital. Case 37-2012. A 21-year-old man with fevers, arthralgias, and pulmonary infiltrates. N Engl J Med. 2012 Nov 29;367(22):2134-46 PMID: 23190225
  3. Chatterjee S, Prayson R, Fraver C. Antisynthetase syndrome: Not just an inflammatory myopathy. Cleveland Clinic Journal of Medicine 2013;80:655-666. PMID: 24085811 - Chatterjee S Mechanic's Hands N Engl J Med 2021; 384:e16. Feb 11 PMID: 33567195 https://www.nejm.org/doi/full/10.1056/NEJMicm2026773
  4. Lazarou IN, Guerne PA Classification, diagnosis, and management of idiopathic inflammatory myopathies. J Rheumatol. 2013 May;40(5):550-64 PMID: 23504386
  5. Lega JC, Fabien N, Reynaud Q et al The clinical phenotype associated with myositis-specific and associated autoantibodies: a meta-analysis revisiting the so-called antisynthetase syndrome. Autoimmun Rev. 2014 Sep;13(9):883-91. Review. PMID: 24704867
  6. Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  7. NEJM Knowledge+