Antisynthetase Syndrome (e.g. Jo-1)
The antisynthetase syndrome is characterized by myositis, interstitial lung disease (ILD), arthritis, mechanic’s hands, and Raynaud’s phenomenon.
This syndrome is seen in myositis patients with antibodies directed against amino-acyl t-RNA synthetases which are in charge of facilitating amino acid binding to its cognate t-RNA. The most common is anti-Jo-1 which is directed against histidyl-tRNA synthetase and is present in 15% to 30% of Adult polymyositis (PM) patients and 10% of Adult dermatomyositis (DM) patients. The other antisynthetase antibodies are in less than 3% to 5% of PM/DM patients. Patients never have more than one of these myositis-specific autoantibodies (MSAs).
The antisynthetase syndrome is characterized by:
Myositis, interstitial lung disease (40% to 90%), Raynaud’s phenomenon (60%), symmetric nonerosive small joint arthritis (60%), mechanic’s hands (70%), and occasionally fever. ANA is typically negative since these MSAs stain cytoplasmic antigens.
The ILD may be the initial presentation and/or predominant symptom in up to 20% of patients.
Some patients also have anti-SSA/Ro antibodies. These patients have worse arthritis and their myositis is more resistant to therapy.
Up to 5% to 8% of antisynthetase syndrome patients have overlap features of another connective tissue disease (SLE, SS, etc.).
Myositis patients with these MSAs rarely if ever have an associated cancer.