musculoskeletal and connective tissue disorders
Autoimmune Myositis
Treatment of Autoimmune Myositis
Corticosteroids Immunosuppressants (eg,methotrexate,azathioprine,mycophenolatemofetil,rituximab,tacrolimus) IV immune globulin Physical activities should be modestly curtailed until the inflammation subsides. Corticosteroids are the drugs of choice initially. For acute disease, adults receive oralprednisone1 mg/kg (usually about 40 to 60 mg) once a day. For severe disease with dysphagia or respiratory muscle weakness, treatment usually starts with high-dose corticosteroid therapy (eg,methylprednisolone0.5 to 1 g IV once a day for 3 to 5 days). Serial measurements of creatine kinase (CK) provide the best early guide of therapeutic effectiveness. However, in patients with widespread muscle atrophy, levels are occasionally normal despite chronic, active myositis. MRI findings of muscle edema or high CK levels generally differentiate a relapse of myositis from corticosteroid-induced myopathy. Aldolase is an alternative, being less specific for muscle injury than CK, but can occasionally be positive in patients with myositis and normal CK levels. As enzyme levels fall toward or reach normal in many patients in 6 to 12 weeks, followed later by improved muscle strength, the corticosteroid dose can be gradually decreased. If muscle enzyme levels rise again, the corticosteroid dose is usually increased while awaiting the full effect of other medications. The overall goal is to rapidly eliminate inflammation but minimize long-term corticosteroid exposure, which is why a second drug (typicallymethotrexate,tacrolimus, orazathioprineas first-line noncorticosteroid drugs) is started at the same time as corticosteroids or shortly after so thatprednisonecan be tapered to a maximum dose of 5 mg a day, ideally within about 6 months. IV immune globulin is a good option for patients who do not respond rapidly to therapy, develop infectious complications with high-dose corticosteroids and other immunosuppressants, or who are undergoing chemotherapy. Some experts may use a combination of all 3 therapies in severe cases or when corticosteroid toxicity is present. Children require initial doses ofprednisoneof 30 to 60 mg/m2once a day. Occasionally, patients treated chronically with high-dose corticosteroids become increasingly weak after the initial response because of a superimposed, painless corticosteroid myopathy. In these patients, CK remains normal even though the patients are weaker. Myositis associated with cancer is more refractory to corticosteroids. Cancer-associated myositis may remit if the tumor is removed. People with an autoimmune disorder are at higher risk of Diagnosis and should be closely monitored. Patients on long-term corticosteroid therapy should receive 