• D Curtin, D Costigan, C McCarthy, M Jansen, M Farrell, V Reid, and K O'Rourke.
• Dublin Neurological Institute at the Mater Misericordiae University Hospital, 57 Eccles St., Dublin 7, Ireland. Denis.Curtin@physicians.ie.
• Ir J Med Sci. 2016 Nov 1; 185 (4): 941-943.

IntroductionThe patient presenting with proximal muscle weakness, elevated serum creatinine kinase and myopathic electromyography and biopsy findings has a wide differential diagnosis that includes toxic, autoimmune, paraneoplastic and congenital myopathies. Autoimmune myopathies are important to identify because they may respond to immunosuppressive therapies.MethodsWe describe two cases of immune-mediated necrotizing myopathy each associated with a novel antibody.ResultsCase 1 describes a progressive myopathy in a statin user. Antibodies to 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase were identified and the patient responded to steroid therapy. Case 2 describes an aggressive myopathy associated with antibodies to signal recognition particle. There was no response to steroids. Clinical improvement followed treatment with rituximab and cyclophosphamide.ConclusionThe identification of myositis-specific antibodies is important because they are associated with distinct clinical phenotypes and may guide the physician in terms of treatment strategies.

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