Monitoring of serum KL-6 antigen in a patient with radiation pneumonia.

Serum marker KL-6 antigen has been reported to be a valuable indicator of the disease activity of interstitial pneumonia. It is not clear how sensitive the serum KL-6 antigen level is in reflecting histologic changes in lung tissues. We report here the results of serial measurements of serum KL-6 antigen in a 76-year-old male patient with radiation pneumonia. Serum KL-6 antigen levels were more sensitive than lactate dehydrogenase and procollagen type III N-terminal peptide. The level of serum KL-6 antigen appears to reflect the histologic changes of the lung more sensitively than does C-reactive protein.