Which of the following antibodies is specific for myositis:

Answer is A(Anti-Jo-1): Anti-Jo-1 Antibodies (Antibodies to histidyl - tRNA) are the most common and most clinically assayed Myositis Specific Antibodies (MSA) Myositis Specific Antibodies (MSA) Myositis Specific antibodies are autoantibodies, usually directed against intracellular ribonucleoproteins that are involved in protein translation. The three best described Myositis Specific Antibodies (MSA) are Anti-Jo-1(directed to t-RNA histidyl-synthetase), Anti-Mi2 and Anti - SRP (Anti Signal Recognition Paicle) The sensitivity of these antibodies is believed to be low Specific MSA are however associated with ceain clinical features and prognosis. M.S.A Association Clinical Features Prognosis Anti-Jo-I Polymyositis * Relatively Acute Onset * Moderate (30% sensitive) * Predicts deforming ahritis, Reynaud's Phenomenon and Pulmonary fibrosis * Moderate Response to therapy but persistent disease Anti-Mi-2 Dermatomyositis * Relatively Acute Onset * Good (5%) sensitive * Predicts classical dermatomyositis rash (`V' sign, Shawl sign) and cuticular over growth * Good response to therapy and good prognosis Anti- SRP Polymyositis / * Very Acute onset * Poor Dermatomyositis (< 5% sensitive) * Predicts severe weakness, palpitations (no rash) * Poor response to therapy and poor prognosis