A 70-year-old man had complained of fever and dry cough for one week. The chest radiograph at his first visit showed right upper lobe opacity. He developed dyspnea and was admitted to our hospital one week later with tachypnea and fever. Fine crackles were heard in the right chest. White blood cell counts (WBC) was 18700/muL (normal: 4000-8000/muL), C-reactive protein (CRP) was 24.2 mg/dL (normal:  0.3 mg/dL). Brain natriuretic peptide, antineutrophil cytoplasmic antibodies (ANCA) and antinuclear antibody (ANA) were normal. Urine antigen testing for Legionella and Streptococcus pneumoniae was negative. Blood gas analysis (BGA) showed hypoxemia with pH 7.43, PaCO2 34 mmHg and PaO2 62 mmHg with oxygen supplementation (2 L) by nasal cannula. High-resolution computed tomography (HRCT) showed ground glass opacities (GGO) in the subpleural upper lobe. His symptoms progressed over a week despite oxygen and antibiotics and repeat HRCT showed air space consolidation with GGO in the right upper and middle lobes with some GGO in the left lung as well (Fig. 1A). The bronchoalveolar lavage fluid (BALF) had a total cell count of 8.4 x 105/mL, with 9% macrophages, 16% lymphocytes, 1% eosinophils, 74% neutrophils and CD4/8 ratio of 1.93. Cytomegalovirus and Pneumocystis jeroveci were negative by polymerase chain reaction (PCR). Transbronchial lung biopsy (TBLB) specimens showed numerous fibrin balls and hyperplasia of type II pneumocytes. Eosinophils, hyaline membranes, and hemosiderin-laden macrophages were absent. Immunohistochemistry of biposy specimens using anti-HO-1 antibody confirmed increased HO-1 in the macrophages within fibrin balls and alveolar walls around fibrin balls (Fig. 2A). Methylpredonisolone pulse therapy was given, 1000 mg/day for 3 days, followed by oral prednisolone (0.5 mg/kg). After two weeks, his symptoms and chest radiograph dramatically improved and pulmonary involvements absolutely disappeared after about 3.7 months without relapse.