Interstitial lung disease is a term that includes dozens of chronic lung disorders. It damages lung tissues, inflames the air sacs, and can permanently scar the tissues between the air sacs. Scarring of these tissues can eventually cause the lung to become stiff.
Researchers find that lung disease may be more common in patients with polymyositis and dermatomyositis than they previously believed. Writing in Current Opinion in Rheumatology, Dr. Maryam Fathi and Dr. Ingrid Lundberg say that high-resolution computerized tomography combined with pulmonary function tests gives the physician better tools for detecting interstitial lung disease, often before the patient exhibits any of the typical symptoms.
Using these diagnostic tools routinely on new PM and DM patients, a recent study found that as many as two-thirds had signs of interstitial lung disease, even though all the patients were in early stages of myositis. PM and DM patients seem to have about the same risk, and the disease is rarely associated with inclusion-body myositis. Recent studies show that patients with amyopathic dermatomyositis (dermatomyositis without the muscle symptoms) are also at risk for lung disease.
There are ways that physicians can predict the likelihood of myositis patients developing interstitial lung disease. Patients with anti-Jo1 antibodies are thought to be at a much higher risk, maybe as high as 70 percent, Drs. Fathi and Lundberg report. Myositis patients with anti-Jo1 antibodies are also more likely to have arthritis, fever, Raynaud's phenomenon, and mechanic's hands.
Detecting the presence of lung disease sooner rather than when symptoms are well established is very important because appropriate treatment may prevent the disease from becoming chronic. In the chronic stage, interstitial lung disease is often called chronic pulmonary fibrosis. Treatment is a complex and individual process, varying according to the patient.
Treatments that appear to be effective, according to Drs. Fathi and Lundberg:
Tacrolimus led to stabilization or improvement in four of five anti-Jo1 antibody-positive patients with polymyositis. These observations were confirmed in a larger patient cohort of 13 patients.
Tumor necrosis factor α (TNF-α) inhibitors have also been mentioned as promising agents for treatment of both myositis and interstitial lung disease.
If you are newly diagnosed with PM or DM, or report any lung-related changes, your doctor may order pulmonary function tests, a number of tests that measure how well the lungs take in and push air out and how efficiently they get oxygen into the blood.
Chest x-rays help physicians detect complications of lung disease and also can identify how the disease is progressing. Fathi and Lundberg note that these tests are not always able to detect early interstitial lung disease, and recommend high-resolution computerized tomography, now widely used for detecting interstitial lung disease, to identify the severity of the disease, and to distinguish between fibrotic disease and active inflammation in the lungs.
Bronchoalveolar lavage is a safe and noninvasive procedure that identifies other causes of interstitial lung disease like infections, drug-induced pneumonitis, and sarcoidosis.
Recently, TMA sponsored a discussion on ILD with Dr. Sonye Danoff, an Assistant Professor in the Division of Pulmonary and Critical Care Medicine and Co-Director of the Hopkins Interstitial Lung Disease Clinic. She also works closely with myositis patients at the Johns Hopkins Myositis Center.
Updated March 2012