Background: A 34-year-old male teacher was referred to the hospital with a persisting dry cough and dyspnea on exercise since eight weeks. He had no fever, neither complaints of ear, nose or throat. There were no complaints during the night. He had been a smoker until four months before presentation (12 pack years). At work a student was diagnosed with pulmonary tuberculosis, but the Mantoux and Quantiferon tests were negative. Physical examination was normal, without fever, lymphadenopathy or auscultation abnormalities. Laboratory investigation revealed a C-reactive protein of 2 mg/L. Pulmonary function testing showed a slight restriction. Immunological bronchial alveolar lavage (BAL) was rich of cells, especially T-lymphocytes of the CD4 type. CD4+/CD8+ ratio of the BAL was raised to 4.2, compared to a ratio of 2.4 in blood. There were no eosinophils found in the BAL. Conventional chest radiographs were performed, and showed multiple areas of consolidation in the bilateral lung fields, predominantly on the right side.