Dyspnea, arthralgias, and muscle weakness
TREATMENT IS WITH STEROIDS AND OTHER IMMUNOSUPPRESSIVES
Oral corticosteroids in dosages of 0.5 to 1 mg/kg are first-line therapy. Clinically, muscle disease often improves before lung disease, and treatment may be extended to several months. The histologic pattern suggested by CT or by pathologic study of surgical lung biopsy specimens is a better predictor of treatment response than clinical presentation. Nonspecific interstitial pneumonitis and organizing pneumonia have the highest steroid response rates.3 However, many patients do not respond to steroids alone—only 44% in one study.5 Furthermore, treatment response does not indicate recovery, as the disease may relapse.
The addition of immunosuppressive therapy with cyclophosphamide (Cytoxan) may halt deterioration in patients with polymyositis-dermatomyositis-associated interstitial lung disease who are steroid-resistant or may be useful as a steroid-sparing agent in recurrent disease after initial steroid withdrawal. In some cases, therapy with cyclophosphamide improved oxygenation and led to resolution of abnormalities on chest radiography.6,7
,Azathioprine (Imuran), methotrexate, and hydroxychloroquine (Plaquenil) have all been used as part of a steroid-sparing regimen.1 Tacrolimus (FK 506; Prograf) and rituximab (Rituxan) are emerging therapies, especially for patients who cannot tolerate cytotoxic immunosuppressive agents or who progress despite them.8,9
PROGNOSIS IS WORSE IF LUNG DISEASE IS PRESENT
The presence of interstitial lung disease increases the risk of death in polymyositis-dermatomyositis. Additionally, clinicians must assess interstitial lung disease separately from muscle or skin disease, as there does not have to be correlation between the activity in the separate organs. Fortunately, the treatment for lung, muscle, and skin involvement is often the same.
Several elements suggest poor prognosis. An acute and aggressive presentation often heralds a poor outcome.1 Neutrophil alveolitis on bronchoalveolar lavage and a very low diffusing capacity (< 45%) have both been associated with a poorer prognosis.3 The histologic pattern not only predicts treatment response but also prognosis. Patients whose lung biopsies reveal nonspecific interstitial pneumonitis or organizing pneumonia have a better outcome than do patients with usual interstitial pneumonia or diffuse alveolar damage.
In one study,1 36 patients with polymyositis-dermatomyositis and interstitial lung disease were followed for 5 years. Resolution was noted in 19.4%, improvement in 55.6%, and deterioration in 25%. Overall, the survival rate was 86.5% at 5 years, and the death rate attributable to pulmonary complications was 13.9% in patients with interstitial lung disease.1
