Lymphoid interstitial pneumonia: clinicopathological and immunopathological findings in 18 cases.

Eighteen patients with lymphoid interstitial pneumonia (LIP) were studied. The diagnosis was established by the microscopic finding of interstitial infiltrates of lymphocytes and plasma cells. Forty-seven% of patients also had germinal centres, while 72% showed interstitial giant cells. Cases studied by the immunoperoxidase technique showed the interstitial plasma cells to be polytypic. The median age of patients was 56 years; most had cough, dyspnea, or chest pain. Chest X-rays showed either patchy interstitial infiltrates (usually bilateral) or poorly defined nodules. Ten patients had hypergammaglobulinemia; one had hypogammaglobulinemia. Two patients had Sjögren's syndrome, two had biopsy-proven chronic active hepatitis, and two had a clinical diagnosis of primary biliary cirrhosis. Follow-up examination of 14 patients showed clearing of symptoms, X-ray infiltrates or stable infiltrates in 4 cases each. Five patients died (mean survival, 41 months), one of whom succumbed to disseminated lymphoma and a second to respiratory failure. Our results support the hypothesis that LIP is a non-neoplastic cellular proliferation in which lymphoma may supervene. The high incidence (22%) of chronic liver disease has not previously been noted.