Lymphocytic interstitial pneumonia associated with a marked increase in monoclonal IgM-kappa-type rheumatoid factor and serum CA19-9.

A 62-year-old Japanese female was admitted due to dyspnea. She showed a marked increase in CA19-9 (maximum, 192,000 U/ml) and monoclonal IgM-kappa type rheumatoid factor (RF) activity. The patient died of respiratory failure 3 months later. Autopsy findings revealed an infiltration of IgM-kappa-positive plasma cells in the pulmonary interstitium, and therefore a diagnosis of lymphoid interstitial pneumonia (LIP) was made. The bronchoepithelial cells were stained with monoclonal antibody-reactive with CA 19-9 antigen. This is the first documented LIP, associated with a marked increase in monoclonal IgM-kappa type RF and CA19-9 in the serum.