Elevation of cytokeratin 19 fragment in patients with interstitial pneumonia associated with polymyositis/dermatomyositis

Objective. Cytokeratin 19 fragment (CK19) levels in serum have been documen ted as a useful tumor marker for lung cancer. We hypothesize that CK19 may increase in serum in patients with interstitial pneumonia associated with p olymyositis/dermatomyositis (PM/DM) and CK19 might be a useful variable to evaluate the activity of lung injury. Methods, 1. We measured CK19 in sera in 15 patients diagnosed with PM/DM; 6 had nonspecific interstitial pneumonia (NIP), 4 had acute interstitial pne umonia (AIP), and 5 had no pulmonary involvement. We also measured CK19 in 10 healthy nonsmokers serving as a control group. 2, We evaluated the corre lation between CK19 level and individual clinical course in patients with p ulmonary involvement associated with PM/DM. Results, CK19 levels in sera of patients with NIP associated with PM/DM wer e significantly higher versus patients with PM/DM without interstitial pneu monia and healthy nonsmokers. CK19 levels in sera in patients with AIP asso ciated with PM/DM were significantly higher compared with the other groups. CK19 values in sera changed according to the progression or improvement of interstitial pneumonia, Immunohistochemical studies using pulmonary tissue s obtained at autopsy from patients with AIP associated with PM/DM revealed that the hyaline membrane was mostly stained by anti-human cytokeratin 19 monoclonal antibody as well as the strong positivity of proliferating type II pneumocytes. Conclusion, These results suggest that the measurement of CK19 was a useful variable to evaluate the activity of lung injury in interstitial pneumonia associated with PM/DM.