[CA19-9-producing idiopathic pulmonary fibrosis with diffuse alveolar damage and  a high titer of KL-6--an autopsy case]. 
A 73-year-old woman with CA19-9-producing idiopathic interstitial pneumonia was admitted to the hospital when her condition was exacerbated. Chest radiography and computed tomography showed an additional patchy shadow. The serum CA19-9 level remained high during the clinical course, whereas KL-6 increased only at exacerbation. No therapy was effective, and the patient died 5 days later. The lung obtained at autopsy showed hyaline membrane formation, hemorrhage, and squamous metaplasia, suggesting that acute exacerbation had resulted in diffuse alveolar damage. Immunohistochemical staining using either anti-CA19-9 mAb or anti-KL-6 mAb showed the localization of CA19-9 and KL-6 antigen in the dilated bronchiolar epithelial cells. In conclusion, although CA19-9 can be an indicator  for the degree of fibrotic and destructive change of lung structure, KL-6 seemed  more sensitively to reflect the disease state of the diffuse alveolar damage.