ACR2012 Highlights: Myositis Diagnosis and Prognosis

December 7, 2012

Among myositis insights at the recent annual meeting: Improving differential diagnosis of inflammatory myopathies, identification and treatment of interstitial lung disease, and optimizing drug treatment.

At the recent American College of Rheumatology meeting, new classification criteria were described that will help distinguish inflammatory myopathies from similar conditions. Identification and treatment of lung comorbidities received great attention, and researchers shared insights into optimizing drug protocols. (Click on the hyperlinks below to read the abstracts of the presentations.)

•   Myositis-associated usual interstitial pneumonia has better survival than idiopathic pulmonary fibrosis. Patients were identified in prospective registries, and death was verified with the Social Security Death Index. Median cumulative survival was 5.2 years in 81 patients with idiopathic disease vs. 16.1 years in 47 patients with myositis-associated disease. (Abstract #217)

•    Aggressive immunomodulatory therapy pays off for myositis patients with interstitial lung disease (ILD). Rheumatologists at Baylor and Houston’s Methodist Hospital examined records of 62 patients with various myopathies treated over the past decade. Among the 22 in whom ILD eventually developed, aggressive treatment with an average of 3 immunomodulatory agents (IVIG plus cyclosporine and sometimes also cyclophosphamide) in addition to corticosteroids produced a direct reversal of the severity of lung disease. (Abstract #219).

•   Lung nodules are not more common in idiopathic inflammatory myopathies than in healthy adults, and are not likely to be cancer. Among 298 patients with at least one CT scan at the Johns Hopkins Myositis Center, 25.5% had nodules, compared to 18% of healthy adults. On followup, none of these nodules increased significantly in size, and half of them decreased. (Abstract #222)

•   Anti-synthetase and Mi-2 antibodies predicted a favorable response of refractory myositis to rituximab. Juvenile dermatomyositis and lower disease damage also predicted a more rapid improvement. These results could identify patients in whom an early, more aggressive treatment would avoid disease-related damage. The Rituximab in Myositis Study evaluated 200 refractory patients over 44 weeks, with a primary endpoint of time to achieve 20% improvement in 3 of 6 core measures. (Abstract #1598)

•    Initiating DMARDs together with steroids as soon as possible after diagnosis of myositis allows the patient to taper the steroid dosage sooner. In a small (61 patient) observational study, rheumatologists from the Netherlands found that patients started on DMARD therapy within 3 months of diagnosis with polymyositis or dermatomyositis were significantly more likely to be able to reduce their dosage of prednisone to below 15 mg. within one year of initiating treatment than those who started either type of drug later. (Abstract #228)

•   The new classification criteria for idiopathic inflammatory myopathies are superior to the old criteria. That’s the internal evaluation of the International Myositis Classification Criteria Project. They are proceeding with an external evaluation. The sensitivity of the risk score is 94%, and specificity is 85%, with muscle biopsy. Two models were developed – a risk score and a classification tree. The risk score performs better than the classification tree, but both performed as well as, or better than, current criteria, in which cases are defined by a specified number of items from a set. This will help distinguish idiopathic inflammatory myopathies from other conditions with which it is easily confused. The criteria were developed from a data set of 973 patients with idiopathic inflammatory myopathy, and 629 comparators. (Abstract #753)