Utilization of myositis antibody-specific panel for diagnosis, treatment, and evaluation of disease progression

The idiopathic inflammatory myopathies (IIM) are rare sporadic disorders with an overall annual incidence of approximately 1 in 100,000 and with a higher incidence in women. IIM is an autoimmune process leading to muscle inflammation due to a 'dysfunctional adaptive immune response evidenced by cell-mediated myocytoxicity, a high prevalence of autoantibodies and overexpression of Major Histocompatibility (MHC) I and II molecules on the muscle sarcolemma'. These autoimmune processes can be appreciated as inflammatory infiltrates in muscle biopsies. Common clinical findings in patients diagnosed with IIM include proximal muscle weakness, elevated creatinine kinase levels, circulating autoantibodies, radiological findings of muscular inflammation, and sometimes edema; in some patients, systemic symptoms such as dysphagia can also be present. Currently, there is no specific IIM classification scheme that incorporates all IIM subtypes; however, the four major IIM subtypes include dermatomyositis, polymyositis, inclusion body myositis, and immune-mediated necrotizing myopathy (IMNM). Two clinical cases are presented in this case report to illustrate a smoldering IIM, antisynthetase syndrome, and a more progressive IIM, anti-signal recognition particle IMNM; highlight the utility of the myositis-specific autoantibody panel for early diagnosis, targeted therapy, and prognosis; and offer primary care providers clues to IIM diagnosis.