pulmonary disorders
Lymphocytic Interstitial Pneumonia
Diagnosis of Lymphocytic Interstitial Pneumonia
High-resolution CT (HRCT) For confirmation, biopsy Diagnosis of lymphocytic interstitial pneumonia is usually suspected in at-risk patients with compatible symptoms. Imaging tests and sometimes lung biopsy are done. Chest x-rayshows bibasilar linear reticular or nodular opacities, a nonspecific finding that is present in a number of pulmonary infections. Alveolar opacities, cysts, or both may be present in more advanced disease. HRCTof the chest is done and helps establish the extent of disease, define the hilar anatomy, and identify pleural involvement. HRCT findings are highly variable. Characteristic findings are centrilobular and subpleural nodules, thickened bronchovascular bundles, nodular ground-glass opacities, and cystic structures. Marked hypoxemia may occur. Bronchoalveolar lavageshould be done to rule out infection and may reveal an increased number of lymphocytes. Routine laboratory testing and serum protein electrophoresis(SPEP)are done because about 80% of patients have a serum protein abnormality, most commonly a polyclonal gammopathy and hypogammaglobulinemia, the significance of which is unknown. Other laboratory tests (eg, serologies, immunoglobulin levels, HIV testing) are obtained to identify potential causes of secondary LIP. Lung biopsywith demonstration of expansion of the alveolar septae due to lymphocytic and other immune cell (plasma cell, immunoblastic, histiocytic) infiltrates is required for diagnosis in adults. Infiltrates appear occasionally along bronchi and vessels but most commonly along alveolar septa. Immunohistochemical staining and flow cytometry must be done on the tissue to distinguish LIP from primary lymphomas. In LIP, the infiltrate is polyclonal (both T and B cells), whereas other lymphomas produce monoclonal infiltrates. Other common findings include germinal centers and multinucleated giant cells with noncaseating granulomas. 