The treatment of inflammatory muscle disorders is largely directed at suppression of the inflammatory response with the aim of protecting viability and function of affected tissues. In this regard, a number of agents have been employed which have both anti-inflammatory and immunomodulatory effects. Corticosteroids, azathioprine, methotrexate, and intravenous gamma globulin have all demonstrated effectiveness and are the most frequently used agents. In addition, cyclosporin, cyclophosphamide and, more recently, biological agents with anti-tumor necrosis action (infliximab, etanercept) as well as the anti-B cell agent rituximab and mycophenolate mofetil have been administered in difficult clinical situations.
With regard to the lung, there is no generally accepted protocol of treatment. Pulmonary disease may precede, occur simultaneously, or appear after the onset of myopathy or skin rash in patients the case of patients with dermatomyositis. The frequency of its occurrence is uncertain but may be as high as affecting one-third of patients. High resolution CT scan and pulmonary function tests are the best approach to early diagnosis. However, weak chest wall musculature resulting in poor ventilatory effort may confound the results of pulmonary function assessment.
Patterns of pulmonary involvement may be variable and include interstitial pneumonia with progressive fibrosis, diffuse alveolitis, and bronchiolitis obliterans with organizing pneumonia. There is an increased frequency of anti-t RNA synthetase antibodies (e.g. J0-1) in these patients. Progressive pulmonary disease is marked by the presence of ground-glass opacities on HRCT and by neutrophilia in bronchoalveolar lavage specimens. Amelioration of pulmonary disease may be achieved with corticosteroids, particularly in patients with the BOOP pattern, as well as with cyclophosphamide. Intravenous gamma globulin has been effective in these patients as well. Azathioprine and methotrexate have also been employed to treat myositis associated pulmonary disease although the possibility of methotrexate-induced interstitial pulmonary disease makes this agent less preferable. The combination of cyclosporin-A and corticosteroids has been reported to be effective in small series of patients.
As might be expected, extensive infiltrates associated with a low diffusing capacity (below 45%) and progressive fibrosis are signs of poor prognosis. Although resolution of abnormalities and stabilization of findings can occur with treatment, some patients experience progression of pulmonary disease. At present, it is not known which factors are responsible for this progression to a poor outcome. Follow-up of patients with pulmonary disorders should include HRCT and PFT's.