Follicular bronchiolitis and lymphocytic interstitial pneumonia in a Japanese man

A transbronchial lung biopsy (TBLB) showed a moderate infiltration of lymphocytes in the alveolar septae. He was diagnosed as interstitial pneumonia, and treated by drugs. One year later, his condition deteriolated, and a large open biopsy was performed. It showed a diffuse severe infiltration of lymphocytes in the alveolar walls and a few epithelioid granulomas. No bronchiolitis was seen.Immunohistochemical study denied lymphocyte monoclonality, and he was diagnosed as lymphocytic interstitial pneumonia (LIP). He was treated by steroid.Six months later, TBLB showed peribronchial lymphocyte infiltration. A large open biopsy also revealed a severe lymphocytic infiltration around the bronchioles, sparing alveolar wall lymphocytic infiltration. Immunohistochemical study denied malignant lymphoma. He was diagnosed as follicular bronchiolitis (FB). One year later, TBLB showed little lymphocytic infiltration in the alveolar walls as well as peribronchial walls. Two years later, his condition became worse, and TBLB showed features of LIP. Later, his condition was stationary for 6 years with mild lung opacities for 6 years. These findings show that LIP and FB are interchangeable and overlapping, and suggest that LIP and FB belong to the same spectrum of benign lymphoproliferative disorders of the lungs.Follicular bronchiolitis (FB) is a benign lymphoproliferative lung disease characterized by hyperplastic mucosa-associated lymphoid tissue present around the peribronchial spaces [1]. Patients with FB are often associated with collagen vasculitis diseases, immunodeficiency state, hyperimmune state, and hereditary factors. Idiopathic FB is rare. Lymphocytic interstitial pneumonia (LIP) is also a benign lymphoproliferative lung disease characterized by severe lymphocytic infiltration of the alveolar septae [1]. Patients with LIP are also often associated with collagen vascular diseases, immunological diseases, immunodeficiency diseases, lung infections, and drug induced disease