Diagnosis and treatment of inflammatory myopathy: issues and management

Abstract

Abstract:The idiopathic inflammatory myopathies include polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM). The specific etiologies of these muscle diseases are not well known and are thought to involve components of the humoral and cellular immune system as well as other nonimmune factors. Diagnosing these myopathies involves a laboratory evaluation, imaging studies, multidisciplinary consultations, histologic examination and potentially genetic studies. Despite all that we currently know about inflammatory muscle disease with these studies, we find that our current concept of muscle disease is changing. In the cases of immune-mediated necrotizing myopathy and inclusion body myositis, the concept of inflammation needs to be rethought. Moreover, the classification schemes for these idiopathic myopathies may need updating to include current research findings that relate to pathogenesis. With ongoing discoveries, classification and appropriate treatment is becoming increasingly challenging. This paper discusses the inflammatory myopathies, the challenges to diagnosis, classification controversies and potential treatment options.

Current pharmacological treatment of idiopathic inflammatory myopathies

“…Although widely prescribed as initial therapy of 1 mg/kg per day for a month, this dosage of prednisolone is probably unnecessary; our group, for example, uses 0.5mg/Kg/day. The dose is then gradually tapered within several weeks to the minimum maintenance dose to keep the disease controlled [6,[17][18][19][20][21]. The rate of taper is dependent on the patient's clinical response [2,6].…”

“…In severe cases, at the onset, methylprednisolone is used intravenously up to 1g per day, for 3-5 days [6,17,18,20].…”

“…Their precise aetiology is unknown and they are characterized by muscle weakness and inflammation, combined with elevated muscle enzymes and characteristic changes on electromyography and muscle biopsy [1,5,[17][18][19].…”

“…The first key to successful treatment is a correct diagnosis [18]. When a patient with DM or PM is not responding to immunosuppressive treatment, physicians must not be afraid to ask themselves if the diagnosis is wrong [3,6,15,16], before considering other therapeutic options [6,15,16].…”

Case Report of Necrotizing Autoimmune Myositis With Slightly High Creatinine Phosphokinase

“…In patients with DM, perifascicular atrophy is common. The main features of IBM include endomysial inflammation, vacuolization ("red rimmed vacuoles" on Gomori trichrome stain), and loss of muscle fibers [10]. Large, atrophic, or angulated fibers are also present.…”