Rheumatoid Arthritis with High Serum KL-6 Complicating Malignant Tumor: Two Case Reports

摘要

Interstitial pneumonia develops not only as a rheumatoid arthritis (RA) manifestation, but also due to the side effects of drugs for its treatment, leading to the necessity of regular examinations. Krebs von den Lungen-6 (KL-6) is often used to check the activity of interstitial pneumonia in RA patients. However, this marker is also produced by some malignant tumors, and a high level of serum KL-6 has been reported in cancer patients. We describe herein 2 cases of RA with the complication of a malignant tumor not involving the lung, although there is no lesion in the lung regardless of the high level of serum KL-6.