Novel antibody associations in immune-mediated necrotising myopathy without inflammation.

INTRODUCTION

The 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.

METHODS

We describe two cases of immune-mediated necrotizing myopathy each associated with a novel antibody.

RESULTS

Case 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.

CONCLUSION

The 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.