|Values are valid only on day of printing.|
Jo 1 (histidyl tRNA synthetase) is a member of the amino acyl-tRNA synthetase family of enzymes found in all nucleated cells. Jo 1 antibodies in patients with polymyositis bind to conformational epitopes of the enzyme protein and inhibit its catalytic activity in vitro.(1)
Jo 1 antibodies are a marker for the disease polymyositis, and occur most commonly in myositis patients who also have interstitial lung disease. The antibodies occur in up to 50% of patients with interstitial pulmonary fibrosis and symmetrical polyarthritis.(2)
See Connective Tissue Disease Cascade (CTDC) in Special Instructions and Optimized Laboratory Testing for Connective Tissue Diseases in Primary Care: The Mayo Connective Tissue Diseases Cascade in Publications.
Evaluating patients with signs and symptoms compatible with a connective tissue disease, especially those patients with muscle pain and limb weakness, concomitant pulmonary signs and symptoms, Raynaudâ€™s phenomenon, and arthritis
A positive result for Jo 1 antibodies is consistent with the diagnosis of polymyositis and suggests an increased risk of pulmonary involvement with fibrosis in such patients.
Testing for antibodies to Jo 1 is not useful in patients with a negative test for antinuclear antibodies.
A negative test for Jo 1 antibodies does not exclude the diagnosis of polymyositis or dermatomyositis.
<1.0 U (negative)
> or =1.0 U (positive)
Reference values apply to all ages.
1. Targoff I: Autoantibodies in polymyositis. Rheum Dis Clin North Am 1992;18:455
2. Leff R, Sherman J, Plotz P: Inflammatory muscle diseases. In Clinical Immunology Principles and Practice, Second edition. Edited by R Rich, T Fleisher, W Shearer, B Kotzin, et al. St. Louis, Mosby-Year Book, 2001, Chapter 65, pp 65.1-65.8